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Merge tag 'audit-pr-20190305' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit
Pull audit updates from Paul Moore:
"A lucky 13 audit patches for v5.1.
Despite the rather large diffstat, most of the changes are from two
bug fix patches that move code from one Kconfig option to another.
Beyond that bit of churn, the remaining changes are largely cleanups
and bug-fixes as we slowly march towards container auditing. It isn't
all boring though, we do have a couple of new things: file
capabilities v3 support, and expanded support for filtering on
filesystems to solve problems with remote filesystems.
All changes pass the audit-testsuite. Please merge for v5.1"
* tag 'audit-pr-20190305' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit:
audit: mark expected switch fall-through
audit: hide auditsc_get_stamp and audit_serial prototypes
audit: join tty records to their syscall
audit: remove audit_context when CONFIG_ AUDIT and not AUDITSYSCALL
audit: remove unused actx param from audit_rule_match
audit: ignore fcaps on umount
audit: clean up AUDITSYSCALL prototypes and stubs
audit: more filter PATH records keyed on filesystem magic
audit: add support for fcaps v3
audit: move loginuid and sessionid from CONFIG_AUDITSYSCALL to CONFIG_AUDIT
audit: add syscall information to CONFIG_CHANGE records
audit: hand taken context to audit_kill_trees for syscall logging
audit: give a clue what CONFIG_CHANGE op was involved
Pull vfs fixes from Al Viro:
"Assorted fixes that sat in -next for a while, all over the place"
* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
aio: Fix locking in aio_poll()
exec: Fix mem leak in kernel_read_file
copy_mount_string: Limit string length to PATH_MAX
cgroup: saner refcounting for cgroup_root
fix cgroup_do_mount() handling of failure exits
This reverts commit 9da3f2b740.
It was well-intentioned, but wrong. Overriding the exception tables for
instructions for random reasons is just wrong, and that is what the new
code did.
It caused problems for tracing, and it caused problems for strncpy_from_user(),
because the new checks made perfectly valid use cases break, rather than
catch things that did bad things.
Unchecked user space accesses are a problem, but that's not a reason to
add invalid checks that then people have to work around with silly flags
(in this case, that 'kernel_uaccess_faults_ok' flag, which is just an
odd way to say "this commit was wrong" and was sprinked into random
places to hide the wrongness).
The real fix to unchecked user space accesses is to get rid of the
special "let's not check __get_user() and __put_user() at all" logic.
Make __{get|put}_user() be just aliases to the regular {get|put}_user()
functions, and make it impossible to access user space without having
the proper checks in places.
The raison d'être of the special double-underscore versions used to be
that the range check was expensive, and if you did multiple user
accesses, you'd do the range check up front (like the signal frame
handling code, for example). But SMAP (on x86) and PAN (on ARM) have
made that optimization pointless, because the _real_ expense is the "set
CPU flag to allow user space access".
Do let's not break the valid cases to catch invalid cases that shouldn't
even exist.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tobin C. Harding <tobin@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On ppc64le, When a string with PAGE_SIZE - 1 (i.e. 64k-1) length is
passed as a "filesystem type" argument to the mount(2) syscall,
copy_mount_string() ends up allocating 64k (the PAGE_SIZE on ppc64le)
worth of space for holding the string in kernel's address space.
Later, in set_precision() (invoked by get_fs_type() ->
__request_module() -> vsnprintf()), we end up assigning
strlen(fs-type-string) i.e. 65535 as the
value to 'struct printf_spec'->precision member. This field has a width
of 16 bits and it is a signed data type. Hence an invalid value ends
up getting assigned. This causes the "WARN_ONCE(spec->precision != prec,
"precision %d too large", prec)" statement inside set_precision() to be
executed.
This commit fixes the bug by limiting the length of the string passed by
copy_mount_string() to strndup_user() to PATH_MAX.
Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
Reported-by: Abdul Haleem <abdhalee@linux.ibm.com>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Don't fetch fcaps when umount2 is called to avoid a process hang while
it waits for the missing resource to (possibly never) re-appear.
Note the comment above user_path_mountpoint_at():
* A umount is a special case for path walking. We're not actually interested
* in the inode in this situation, and ESTALE errors can be a problem. We
* simply want track down the dentry and vfsmount attached at the mountpoint
* and avoid revalidating the last component.
This can happen on ceph, cifs, 9p, lustre, fuse (gluster) or NFS.
Please see the github issue tracker
https://github.com/linux-audit/audit-kernel/issues/100
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
[PM: merge fuzz in audit_log_fcaps()]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Pull vfs mount API prep from Al Viro:
"Mount API prereqs.
Mostly that's LSM mount options cleanups. There are several minor
fixes in there, but nothing earth-shattering (leaks on failure exits,
mostly)"
* 'mount.part1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (27 commits)
mount_fs: suppress MAC on MS_SUBMOUNT as well as MS_KERNMOUNT
smack: rewrite smack_sb_eat_lsm_opts()
smack: get rid of match_token()
smack: take the guts of smack_parse_opts_str() into a new helper
LSM: new method: ->sb_add_mnt_opt()
selinux: rewrite selinux_sb_eat_lsm_opts()
selinux: regularize Opt_... names a bit
selinux: switch away from match_token()
selinux: new helper - selinux_add_opt()
LSM: bury struct security_mnt_opts
smack: switch to private smack_mnt_opts
selinux: switch to private struct selinux_mnt_opts
LSM: hide struct security_mnt_opts from any generic code
selinux: kill selinux_sb_get_mnt_opts()
LSM: turn sb_eat_lsm_opts() into a method
nfs_remount(): don't leak, don't ignore LSM options quietly
btrfs: sanitize security_mnt_opts use
selinux; don't open-code a loop in sb_finish_set_opts()
LSM: split ->sb_set_mnt_opts() out of ->sb_kern_mount()
new helper: security_sb_eat_lsm_opts()
...
Pull trivial vfs updates from Al Viro:
"A few cleanups + Neil's namespace_unlock() optimization"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
exec: make prepare_bprm_creds static
genheaders: %-<width>s had been there since v6; %-*s - since v7
VFS: use synchronize_rcu_expedited() in namespace_unlock()
iov_iter: reduce code duplication
Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument
of the user address range verification function since we got rid of the
old racy i386-only code to walk page tables by hand.
It existed because the original 80386 would not honor the write protect
bit when in kernel mode, so you had to do COW by hand before doing any
user access. But we haven't supported that in a long time, and these
days the 'type' argument is a purely historical artifact.
A discussion about extending 'user_access_begin()' to do the range
checking resulted this patch, because there is no way we're going to
move the old VERIFY_xyz interface to that model. And it's best done at
the end of the merge window when I've done most of my merges, so let's
just get this done once and for all.
This patch was mostly done with a sed-script, with manual fix-ups for
the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form.
There were a couple of notable cases:
- csky still had the old "verify_area()" name as an alias.
- the iter_iov code had magical hardcoded knowledge of the actual
values of VERIFY_{READ,WRITE} (not that they mattered, since nothing
really used it)
- microblaze used the type argument for a debug printout
but other than those oddities this should be a total no-op patch.
I tried to fix up all architectures, did fairly extensive grepping for
access_ok() uses, and the changes are trivial, but I may have missed
something. Any missed conversion should be trivially fixable, though.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Keep void * instead, allocate on demand (in parse_str_opts, at the
moment). Eventually both selinux and smack will be better off
with private structures with several strings in those, rather than
this "counter and two pointers to dynamically allocated arrays"
ugliness. This commit allows to do that at leisure, without
disrupting anything outside of given module.
Changes:
* instead of struct security_mnt_opt use an opaque pointer
initialized to NULL.
* security_sb_eat_lsm_opts(), security_sb_parse_opts_str() and
security_free_mnt_opts() take it as var argument (i.e. as void **);
call sites are unchanged.
* security_sb_set_mnt_opts() and security_sb_remount() take
it by value (i.e. as void *).
* new method: ->sb_free_mnt_opts(). Takes void *, does
whatever freeing that needs to be done.
* ->sb_set_mnt_opts() and ->sb_remount() might get NULL as
mnt_opts argument, meaning "empty".
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
combination of alloc_secdata(), security_sb_copy_data(),
security_sb_parse_opt_str() and free_secdata().
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This paves the way for retaining the LSM options from a common filesystem
mount context during a mount parameter parsing phase to be instituted prior
to actual mount/reconfiguration actions.
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Separate just the changing of mount flags (MS_REMOUNT|MS_BIND) from full
remount because the mount data will get parsed with the new fs_context
stuff prior to doing a remount - and this causes the syscall to fail under
some circumstances.
To quote Eric's explanation:
[...] mount(..., MS_REMOUNT|MS_BIND, ...) now validates the mount options
string, which breaks systemd unit files with ProtectControlGroups=yes
(e.g. systemd-networkd.service) when systemd does the following to
change a cgroup (v1) mount to read-only:
mount(NULL, "/run/systemd/unit-root/sys/fs/cgroup/systemd", NULL,
MS_RDONLY|MS_NOSUID|MS_NODEV|MS_NOEXEC|MS_REMOUNT|MS_BIND, NULL)
... when the kernel has CONFIG_CGROUPS=y but no cgroup subsystems
enabled, since in that case the error "cgroup1: Need name or subsystem
set" is hit when the mount options string is empty.
Probably it doesn't make sense to validate the mount options string at
all in the MS_REMOUNT|MS_BIND case, though maybe you had something else
in mind.
This is also worthwhile doing because we will need to add a mount_setattr()
syscall to take over the remount-bind function.
Reported-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: David Howells <dhowells@redhat.com>
Only the mount namespace code that implements mount(2) should be using the
MS_* flags. Suppress them inside the kernel unless uapi/linux/mount.h is
included.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: David Howells <dhowells@redhat.com>
The synchronize_rcu() in namespace_unlock() is called every time
a filesystem is unmounted. If a great many filesystems are mounted,
this can cause a noticable slow-down in, for example, system shutdown.
The sequence:
mkdir -p /tmp/Mtest/{0..5000}
time for i in /tmp/Mtest/*; do mount -t tmpfs tmpfs $i ; done
time umount /tmp/Mtest/*
on a 4-cpu VM can report 8 seconds to mount the tmpfs filesystems, and
100 seconds to unmount them.
Boot the same VM with 1 CPU and it takes 18 seconds to mount the
tmpfs filesystems, but only 36 to unmount.
If we change the synchronize_rcu() to synchronize_rcu_expedited()
the umount time on a 4-cpu VM drop to 0.6 seconds
I think this 200-fold speed up is worth the slightly high system
impact of using synchronize_rcu_expedited().
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> (from general rcu perspective)
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Since commit ff17fa561a ("d_invalidate(): unhash immediately")
immediately unhashes the dentry, we'll never return the mountpoint in
lookup_mountpoint(), which can lead to an unbreakable loop in
d_invalidate().
I have reports of NFS clients getting into this condition after the server
removes an export of an existing mount created through follow_automount(),
but I suspect there are various other ways to produce this problem if we
hunt down users of d_invalidate(). For example, it is possible to get into
this state by using XFS' d_invalidate() call in xfs_vn_unlink():
truncate -s 100m img{1,2}
mkfs.xfs -q -n version=ci img1
mkfs.xfs -q -n version=ci img2
mkdir -p /mnt/xfs
mount img1 /mnt/xfs
mkdir /mnt/xfs/sub1
mount img2 /mnt/xfs/sub1
cat > /mnt/xfs/sub1/foo &
umount -l /mnt/xfs/sub1
mount img2 /mnt/xfs/sub1
mount --make-private /mnt/xfs
mkdir /mnt/xfs/sub2
mount --move /mnt/xfs/sub1 /mnt/xfs/sub2
rmdir /mnt/xfs/sub1
Fix this by moving the check for an unlinked dentry out of the
detach_mounts() path.
Fixes: ff17fa561a ("d_invalidate(): unhash immediately")
Cc: stable@vger.kernel.org
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Timothy Baldwin <timbaldwin@fastmail.co.uk> wrote:
> As per mount_namespaces(7) unprivileged users should not be able to look under mount points:
>
> Mounts that come as a single unit from more privileged mount are locked
> together and may not be separated in a less privileged mount namespace.
>
> However they can:
>
> 1. Create a mount namespace.
> 2. In the mount namespace open a file descriptor to the parent of a mount point.
> 3. Destroy the mount namespace.
> 4. Use the file descriptor to look under the mount point.
>
> I have reproduced this with Linux 4.16.18 and Linux 4.18-rc8.
>
> The setup:
>
> $ sudo sysctl kernel.unprivileged_userns_clone=1
> kernel.unprivileged_userns_clone = 1
> $ mkdir -p A/B/Secret
> $ sudo mount -t tmpfs hide A/B
>
>
> "Secret" is indeed hidden as expected:
>
> $ ls -lR A
> A:
> total 0
> drwxrwxrwt 2 root root 40 Feb 12 21:08 B
>
> A/B:
> total 0
>
>
> The attack revealing "Secret":
>
> $ unshare -Umr sh -c "exec unshare -m ls -lR /proc/self/fd/4/ 4<A"
> /proc/self/fd/4/:
> total 0
> drwxr-xr-x 3 root root 60 Feb 12 21:08 B
>
> /proc/self/fd/4/B:
> total 0
> drwxr-xr-x 2 root root 40 Feb 12 21:08 Secret
>
> /proc/self/fd/4/B/Secret:
> total 0
I tracked this down to put_mnt_ns running passing UMOUNT_SYNC and
disconnecting all of the mounts in a mount namespace. Fix this by
factoring drop_mounts out of drop_collected_mounts and passing
0 instead of UMOUNT_SYNC.
There are two possible behavior differences that result from this.
- No longer setting UMOUNT_SYNC will no longer set MNT_SYNC_UMOUNT on
the vfsmounts being unmounted. This effects the lazy rcu walk by
kicking the walk out of rcu mode and forcing it to be a non-lazy
walk.
- No longer disconnecting locked mounts will keep some mounts around
longer as they stay because the are locked to other mounts.
There are only two users of drop_collected mounts: audit_tree.c and
put_mnt_ns.
In audit_tree.c the mounts are private and there are no rcu lazy walks
only calls to iterate_mounts. So the changes should have no effect
except for a small timing effect as the connected mounts are disconnected.
In put_mnt_ns there may be references from process outside the mount
namespace to the mounts. So the mounts remaining connected will
be the bug fix that is needed. That rcu walks are allowed to continue
appears not to be a problem especially as the rcu walk change was about
an implementation detail not about semantics.
Cc: stable@vger.kernel.org
Fixes: 5ff9d8a65c ("vfs: Lock in place mounts from more privileged users")
Reported-by: Timothy Baldwin <timbaldwin@fastmail.co.uk>
Tested-by: Timothy Baldwin <timbaldwin@fastmail.co.uk>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Jonathan Calmels from NVIDIA reported that he's able to bypass the
mount visibility security check in place in the Linux kernel by using
a combination of the unbindable property along with the private mount
propagation option to allow a unprivileged user to see a path which
was purposefully hidden by the root user.
Reproducer:
# Hide a path to all users using a tmpfs
root@castiana:~# mount -t tmpfs tmpfs /sys/devices/
root@castiana:~#
# As an unprivileged user, unshare user namespace and mount namespace
stgraber@castiana:~$ unshare -U -m -r
# Confirm the path is still not accessible
root@castiana:~# ls /sys/devices/
# Make /sys recursively unbindable and private
root@castiana:~# mount --make-runbindable /sys
root@castiana:~# mount --make-private /sys
# Recursively bind-mount the rest of /sys over to /mnnt
root@castiana:~# mount --rbind /sys/ /mnt
# Access our hidden /sys/device as an unprivileged user
root@castiana:~# ls /mnt/devices/
breakpoint cpu cstate_core cstate_pkg i915 intel_pt isa kprobe
LNXSYSTM:00 msr pci0000:00 platform pnp0 power software system
tracepoint uncore_arb uncore_cbox_0 uncore_cbox_1 uprobe virtual
Solve this by teaching copy_tree to fail if a mount turns out to be
both unbindable and locked.
Cc: stable@vger.kernel.org
Fixes: 5ff9d8a65c ("vfs: Lock in place mounts from more privileged users")
Reported-by: Jonathan Calmels <jcalmels@nvidia.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
It was recently pointed out that the one instance of testing MNT_LOCKED
outside of the namespace_sem is in ksys_umount.
Fix that by adding a test inside of do_umount with namespace_sem and
the mount_lock held. As it helps to fail fails the existing test is
maintained with an additional comment pointing out that it may be racy
because the locks are not held.
Cc: stable@vger.kernel.org
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Fixes: 5ff9d8a65c ("vfs: Lock in place mounts from more privileged users")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Move remaining definitions and declarations from include/linux/bootmem.h
into include/linux/memblock.h and remove the redundant header.
The includes were replaced with the semantic patch below and then
semi-automated removal of duplicated '#include <linux/memblock.h>
@@
@@
- #include <linux/bootmem.h>
+ #include <linux/memblock.h>
[sfr@canb.auug.org.au: dma-direct: fix up for the removal of linux/bootmem.h]
Link: http://lkml.kernel.org/r/20181002185342.133d1680@canb.auug.org.au
[sfr@canb.auug.org.au: powerpc: fix up for removal of linux/bootmem.h]
Link: http://lkml.kernel.org/r/20181005161406.73ef8727@canb.auug.org.au
[sfr@canb.auug.org.au: x86/kaslr, ACPI/NUMA: fix for linux/bootmem.h removal]
Link: http://lkml.kernel.org/r/20181008190341.5e396491@canb.auug.org.au
Link: http://lkml.kernel.org/r/1536927045-23536-30-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guan Xuetao <gxt@pku.edu.cn>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Serge Semin <fancer.lancer@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There have been multiple kernel vulnerabilities that permitted userspace to
pass completely unchecked pointers through to userspace accessors:
- the waitid() bug - commit 96ca579a1e ("waitid(): Add missing
access_ok() checks")
- the sg/bsg read/write APIs
- the infiniband read/write APIs
These don't happen all that often, but when they do happen, it is hard to
test for them properly; and it is probably also hard to discover them with
fuzzing. Even when an unmapped kernel address is supplied to such buggy
code, it just returns -EFAULT instead of doing a proper BUG() or at least
WARN().
Try to make such misbehaving code a bit more visible by refusing to do a
fixup in the pagefault handler code when a userspace accessor causes a #PF
on a kernel address and the current context isn't whitelisted.
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: kernel-hardening@lists.openwall.com
Cc: dvyukov@google.com
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Borislav Petkov <bp@alien8.de>
Link: https://lkml.kernel.org/r/20180828201421.157735-7-jannh@google.com
Pull IDA updates from Matthew Wilcox:
"A better IDA API:
id = ida_alloc(ida, GFP_xxx);
ida_free(ida, id);
rather than the cumbersome ida_simple_get(), ida_simple_remove().
The new IDA API is similar to ida_simple_get() but better named. The
internal restructuring of the IDA code removes the bitmap
preallocation nonsense.
I hope the net -200 lines of code is convincing"
* 'ida-4.19' of git://git.infradead.org/users/willy/linux-dax: (29 commits)
ida: Change ida_get_new_above to return the id
ida: Remove old API
test_ida: check_ida_destroy and check_ida_alloc
test_ida: Convert check_ida_conv to new API
test_ida: Move ida_check_max
test_ida: Move ida_check_leaf
idr-test: Convert ida_check_nomem to new API
ida: Start new test_ida module
target/iscsi: Allocate session IDs from an IDA
iscsi target: fix session creation failure handling
drm/vmwgfx: Convert to new IDA API
dmaengine: Convert to new IDA API
ppc: Convert vas ID allocation to new IDA API
media: Convert entity ID allocation to new IDA API
ppc: Convert mmu context allocation to new IDA API
Convert net_namespace to new IDA API
cb710: Convert to new IDA API
rsxx: Convert to new IDA API
osd: Convert to new IDA API
sd: Convert to new IDA API
...
This contains two new features:
1) Stack file operations: this allows removal of several hacks from the
VFS, proper interaction of read-only open files with copy-up,
possibility to implement fs modifying ioctls properly, and others.
2) Metadata only copy-up: when file is on lower layer and only metadata is
modified (except size) then only copy up the metadata and continue to
use the data from the lower file.
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Merge tag 'ovl-update-4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull overlayfs updates from Miklos Szeredi:
"This contains two new features:
- Stack file operations: this allows removal of several hacks from
the VFS, proper interaction of read-only open files with copy-up,
possibility to implement fs modifying ioctls properly, and others.
- Metadata only copy-up: when file is on lower layer and only
metadata is modified (except size) then only copy up the metadata
and continue to use the data from the lower file"
* tag 'ovl-update-4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs: (66 commits)
ovl: Enable metadata only feature
ovl: Do not do metacopy only for ioctl modifying file attr
ovl: Do not do metadata only copy-up for truncate operation
ovl: add helper to force data copy-up
ovl: Check redirect on index as well
ovl: Set redirect on upper inode when it is linked
ovl: Set redirect on metacopy files upon rename
ovl: Do not set dentry type ORIGIN for broken hardlinks
ovl: Add an inode flag OVL_CONST_INO
ovl: Treat metacopy dentries as type OVL_PATH_MERGE
ovl: Check redirects for metacopy files
ovl: Move some dir related ovl_lookup_single() code in else block
ovl: Do not expose metacopy only dentry from d_real()
ovl: Open file with data except for the case of fsync
ovl: Add helper ovl_inode_realdata()
ovl: Store lower data inode in ovl_inode
ovl: Fix ovl_getattr() to get number of blocks from lower
ovl: Add helper ovl_dentry_lowerdata() to get lower data dentry
ovl: Copy up meta inode data from lowest data inode
ovl: Modify ovl_lookup() and friends to lookup metacopy dentry
...
__legitimize_mnt() has two problems - one is that in case of success
the check of mount_lock is not ordered wrt preceding increment of
refcount, making it possible to have successful __legitimize_mnt()
on one CPU just before the otherwise final mntpu() on another,
with __legitimize_mnt() not seeing mntput() taking the lock and
mntput() not seeing the increment done by __legitimize_mnt().
Solved by a pair of barriers.
Another is that failure of __legitimize_mnt() on the second
read_seqretry() leaves us with reference that'll need to be
dropped by caller; however, if that races with final mntput()
we can end up with caller dropping rcu_read_lock() and doing
mntput() to release that reference - with the first mntput()
having freed the damn thing just as rcu_read_lock() had been
dropped. Solution: in "do mntput() yourself" failure case
grab mount_lock, check if MNT_DOOMED has been set by racing
final mntput() that has missed our increment and if it has -
undo the increment and treat that as "failure, caller doesn't
need to drop anything" case.
It's not easy to hit - the final mntput() has to come right
after the first read_seqretry() in __legitimize_mnt() *and*
manage to miss the increment done by __legitimize_mnt() before
the second read_seqretry() in there. The things that are almost
impossible to hit on bare hardware are not impossible on SMP
KVM, though...
Reported-by: Oleg Nesterov <oleg@redhat.com>
Fixes: 48a066e72d ("RCU'd vsfmounts")
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
mntput_no_expire() does the calculation of total refcount under mount_lock;
unfortunately, the decrement (as well as all increments) are done outside
of it, leading to false positives in the "are we dropping the last reference"
test. Consider the following situation:
* mnt is a lazy-umounted mount, kept alive by two opened files. One
of those files gets closed. Total refcount of mnt is 2. On CPU 42
mntput(mnt) (called from __fput()) drops one reference, decrementing component
* After it has looked at component #0, the process on CPU 0 does
mntget(), incrementing component #0, gets preempted and gets to run again -
on CPU 69. There it does mntput(), which drops the reference (component #69)
and proceeds to spin on mount_lock.
* On CPU 42 our first mntput() finishes counting. It observes the
decrement of component #69, but not the increment of component #0. As the
result, the total it gets is not 1 as it should've been - it's 0. At which
point we decide that vfsmount needs to be killed and proceed to free it and
shut the filesystem down. However, there's still another opened file
on that filesystem, with reference to (now freed) vfsmount, etc. and we are
screwed.
It's not a wide race, but it can be reproduced with artificial slowdown of
the mnt_get_count() loop, and it should be easier to hit on SMP KVM setups.
Fix consists of moving the refcount decrement under mount_lock; the tricky
part is that we want (and can) keep the fast case (i.e. mount that still
has non-NULL ->mnt_ns) entirely out of mount_lock. All places that zero
mnt->mnt_ns are dropping some reference to mnt and they call synchronize_rcu()
before that mntput(). IOW, if mntput() observes (under rcu_read_lock())
a non-NULL ->mnt_ns, it is guaranteed that there is another reference yet to
be dropped.
Reported-by: Jann Horn <jannh@google.com>
Tested-by: Jann Horn <jannh@google.com>
Fixes: 48a066e72d ("RCU'd vsfmounts")
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The underlying real file used by overlayfs still contains the overlay path.
This results in mnt_want_write_file() calls by the filesystem getting
freeze protection on the wrong inode (the overlayfs one instead of the real
one).
Fix by using file_inode(file)->i_sb instead of file->f_path.mnt->mnt_sb.
Reported-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This reverts commit 7c6893e3c9.
Overlayfs no longer relies on the vfs for checking writability of files.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This reverts commit 954c736f86.
Overlayfs no longer relies on the vfs for checking writability of files.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Superblock level remounts are currently restricted to global
CAP_SYS_ADMIN, as is the path for changing the root mount to
read only on umount. Loosen both of these permission checks to
also allow CAP_SYS_ADMIN in any namespace which is privileged
towards the userns which originally mounted the filesystem.
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Acked-by: Christian Brauner <christian@brauner.io>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
In do_mount() when the MS_* flags are being converted to MNT_* flags,
MS_RDONLY got accidentally convered to SB_RDONLY.
Undo this change.
Fixes: e462ec50cb ("VFS: Differentiate mount flags (MS_*) from internal superblock flags")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We want it only for the stuff created by SB_KERNMOUNT mounts, *not* for
their copies. As it is, creating a deep stack of bindings of /proc/*/ns/*
somewhere in a new namespace and exiting yields a stack overflow.
Cc: stable@kernel.org
Reported-by: Alexander Aring <aring@mojatatu.com>
Bisected-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Tested-by: Alexander Aring <aring@mojatatu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Using this helper allows us to avoid the in-kernel call to the sys_umount()
syscall. The ksys_ prefix denotes that this function is meant as a drop-in
replacement for the syscall. In particular, it uses the same calling
convention as ksys_umount().
In the near future, the only fs-external caller of ksys_umount() should be
converted to call do_umount() directly. Then, ksys_umount() can be moved
within sys_umount() again.
This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Using this helper allows us to avoid the in-kernel calls to the sys_mount()
syscall. The ksys_ prefix denotes that this function is meant as a drop-in
replacement for the syscall. In particular, it uses the same calling
convention as sys_mount().
In the near future, all callers of ksys_mount() should be converted to call
do_mount() directly.
This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Since commit e462ec50cb ("VFS: Differentiate mount flags (MS_*) from
internal superblock flags") the lazytime mount option doesn't get passed
on anymore.
Fix the issue by handling the option in do_mount().
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Please do not apply this to mainline directly, instead please re-run the
coccinelle script shown below and apply its output.
For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't harmful, and changing them results in
churn.
However, for some features, the read/write distinction is critical to
correct operation. To distinguish these cases, separate read/write
accessors must be used. This patch migrates (most) remaining
ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following
coccinelle script:
----
// Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and
// WRITE_ONCE()
// $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch
virtual patch
@ depends on patch @
expression E1, E2;
@@
- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)
@ depends on patch @
expression E;
@@
- ACCESS_ONCE(E)
+ READ_ONCE(E)
----
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The mount i_version flag is not enabled in the new sb_flags. This patch
adds the missing SB_I_VERSION flag.
Fixes: e462ec5 "VFS: Differentiate mount flags (MS_*) from internal
superblock flags"
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Overlayfs directory file_inode() is the overlay inode whether the real
inode is upper or lower.
This fixes a regression in xfstest generic/158.
Fixes: 7c6893e3c9 ("ovl: don't allow writing ioctl on lower layer")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Pull misc leftovers from Al Viro.
* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fix the __user misannotations in asm-generic get_user/put_user
fput: Don't reinvent the wheel but use existing llist API
namespace.c: Don't reinvent the wheel but use existing llist API
Pull mount flag updates from Al Viro:
"Another chunk of fmount preparations from dhowells; only trivial
conflicts for that part. It separates MS_... bits (very grotty
mount(2) ABI) from the struct super_block ->s_flags (kernel-internal,
only a small subset of MS_... stuff).
This does *not* convert the filesystems to new constants; only the
infrastructure is done here. The next step in that series is where the
conflicts would be; that's the conversion of filesystems. It's purely
mechanical and it's better done after the merge, so if you could run
something like
list=$(for i in MS_RDONLY MS_NOSUID MS_NODEV MS_NOEXEC MS_SYNCHRONOUS MS_MANDLOCK MS_DIRSYNC MS_NOATIME MS_NODIRATIME MS_SILENT MS_POSIXACL MS_KERNMOUNT MS_I_VERSION MS_LAZYTIME; do git grep -l $i fs drivers/staging/lustre drivers/mtd ipc mm include/linux; done|sort|uniq|grep -v '^fs/namespace.c$')
sed -i -e 's/\<MS_RDONLY\>/SB_RDONLY/g' \
-e 's/\<MS_NOSUID\>/SB_NOSUID/g' \
-e 's/\<MS_NODEV\>/SB_NODEV/g' \
-e 's/\<MS_NOEXEC\>/SB_NOEXEC/g' \
-e 's/\<MS_SYNCHRONOUS\>/SB_SYNCHRONOUS/g' \
-e 's/\<MS_MANDLOCK\>/SB_MANDLOCK/g' \
-e 's/\<MS_DIRSYNC\>/SB_DIRSYNC/g' \
-e 's/\<MS_NOATIME\>/SB_NOATIME/g' \
-e 's/\<MS_NODIRATIME\>/SB_NODIRATIME/g' \
-e 's/\<MS_SILENT\>/SB_SILENT/g' \
-e 's/\<MS_POSIXACL\>/SB_POSIXACL/g' \
-e 's/\<MS_KERNMOUNT\>/SB_KERNMOUNT/g' \
-e 's/\<MS_I_VERSION\>/SB_I_VERSION/g' \
-e 's/\<MS_LAZYTIME\>/SB_LAZYTIME/g' \
$list
and commit it with something along the lines of 'convert filesystems
away from use of MS_... constants' as commit message, it would save a
quite a bit of headache next cycle"
* 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
VFS: Differentiate mount flags (MS_*) from internal superblock flags
VFS: Convert sb->s_flags & MS_RDONLY to sb_rdonly(sb)
vfs: Add sb_rdonly(sb) to query the MS_RDONLY flag on s_flags
Problem with ioctl() is that it's a file operation, yet often used as an
inode operation (i.e. modify the inode despite the file being opened for
read-only).
mnt_want_write_file() is used by filesystems in such cases to get write
access on an arbitrary open file.
Since overlayfs lets filesystems do all file operations, including ioctl,
this can lead to mnt_want_write_file() returning OK for a lower file and
modification of that lower file.
This patch prevents modification by checking if the file is from an
overlayfs lower layer and returning EPERM in that case.
Need to introduce a mnt_want_write_file_path() variant that still does the
old thing for inode operations that can do the copy up + modification
correctly in such cases (fchown, fsetxattr, fremovexattr).
This does not address the correctness of such ioctls on overlayfs (the
correct way would be to copy up and attempt to perform ioctl on upper
file).
In theory this could be a regression. We very much hope that nobody is
relying on such a hack in any sane setup.
While this patch meddles in VFS code, it has no effect on non-overlayfs
filesystems.
Reported-by: "zhangyi (F)" <yi.zhang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Although llist provides proper APIs, they are not used. Make them used.
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Differentiate the MS_* flags passed to mount(2) from the internal flags set
in the super_block's s_flags. s_flags are now called SB_*, with the names
and the values for the moment mirroring the MS_* flags that they're
equivalent to.
In this patch, just the headers are altered and some kernel code where
blind automated conversion isn't necessarily correct.
Note that this shows up some interesting issues:
(1) Some MS_* flags get translated to MNT_* flags (such as MS_NODEV ->
MNT_NODEV) without passing this on to the filesystem, but some
filesystems set such flags anyway.
(2) The ->remount_fs() methods of some filesystems adjust the *flags
argument by setting MS_* flags in it, such as MS_NOATIME - but these
flags are then scrubbed by do_remount_sb() (only the occupants of
MS_RMT_MASK are permitted: MS_RDONLY, MS_SYNCHRONOUS, MS_MANDLOCK,
MS_I_VERSION and MS_LAZYTIME)
I'm not sure what's the best way to solve all these cases.
Suggested-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
Firstly by applying the following with coccinelle's spatch:
@@ expression SB; @@
-SB->s_flags & MS_RDONLY
+sb_rdonly(SB)
to effect the conversion to sb_rdonly(sb), then by applying:
@@ expression A, SB; @@
(
-(!sb_rdonly(SB)) && A
+!sb_rdonly(SB) && A
|
-A != (sb_rdonly(SB))
+A != sb_rdonly(SB)
|
-A == (sb_rdonly(SB))
+A == sb_rdonly(SB)
|
-!(sb_rdonly(SB))
+!sb_rdonly(SB)
|
-A && (sb_rdonly(SB))
+A && sb_rdonly(SB)
|
-A || (sb_rdonly(SB))
+A || sb_rdonly(SB)
|
-(sb_rdonly(SB)) != A
+sb_rdonly(SB) != A
|
-(sb_rdonly(SB)) == A
+sb_rdonly(SB) == A
|
-(sb_rdonly(SB)) && A
+sb_rdonly(SB) && A
|
-(sb_rdonly(SB)) || A
+sb_rdonly(SB) || A
)
@@ expression A, B, SB; @@
(
-(sb_rdonly(SB)) ? 1 : 0
+sb_rdonly(SB)
|
-(sb_rdonly(SB)) ? A : B
+sb_rdonly(SB) ? A : B
)
to remove left over excess bracketage and finally by applying:
@@ expression A, SB; @@
(
-(A & MS_RDONLY) != sb_rdonly(SB)
+(bool)(A & MS_RDONLY) != sb_rdonly(SB)
|
-(A & MS_RDONLY) == sb_rdonly(SB)
+(bool)(A & MS_RDONLY) == sb_rdonly(SB)
)
to make comparisons against the result of sb_rdonly() (which is a bool)
work correctly.
Signed-off-by: David Howells <dhowells@redhat.com>
Pull ->s_options removal from Al Viro:
"Preparations for fsmount/fsopen stuff (coming next cycle). Everything
gets moved to explicit ->show_options(), killing ->s_options off +
some cosmetic bits around fs/namespace.c and friends. Basically, the
stuff needed to work with fsmount series with minimum of conflicts
with other work.
It's not strictly required for this merge window, but it would reduce
the PITA during the coming cycle, so it would be nice to have those
bits and pieces out of the way"
* 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
isofs: Fix isofs_show_options()
VFS: Kill off s_options and helpers
orangefs: Implement show_options
9p: Implement show_options
isofs: Implement show_options
afs: Implement show_options
affs: Implement show_options
befs: Implement show_options
spufs: Implement show_options
bpf: Implement show_options
ramfs: Implement show_options
pstore: Implement show_options
omfs: Implement show_options
hugetlbfs: Implement show_options
VFS: Don't use save/replace_mount_options if not using generic_show_options
VFS: Provide empty name qstr
VFS: Make get_filesystem() return the affected filesystem
VFS: Clean up whitespace in fs/namespace.c and fs/super.c
Provide a function to create a NUL-terminated string from unterminated data
Kill off s_options, save/replace_mount_options() and generic_show_options()
as all filesystems now implement ->show_options() for themselves. This
should make it easier to implement a context-based mount where the mount
options can be passed individually over a file descriptor.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Clean up line terminal whitespace in fs/namespace.c and fs/super.c.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull mnt namespace updates from Eric Biederman:
"A big break-through came during this development cycle as a way was
found to maintain the existing umount -l semantics while allowing for
optimizations that improve the performance. That is represented by the
first change in this series moving the reparenting of mounts into
their own pass. This has allowed addressing the horrific performance
of umount -l on a carefully crafted tree of mounts with locks held
(0.06s vs 60s in my testing). What allowed this was not changing where
umounts propagate to while propgating umounts.
The next change fixes the case where the order of the mount whose
umount are being progated visits a tree where the mounts are stacked
upon each other in another order. This is weird but not hard to
implement.
The final change takes advantage of the unchanging mount propgation
tree to skip parts of the mount propgation tree that have already been
visited. Yielding a very nice speed up in the worst case.
There remains one outstanding question about the semantics of umount -l
that I am still discussiong with Ram Pai. In practice that area of the
semantics was changed by 1064f874ab ("mnt: Tuck mounts under others
instead of creating shadow/side mounts.") and no regressions have been
reported. Still I intend to finish talking that out with him to ensure
there is not something a more intense use of mount propagation in the
future will not cause to become significant"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
mnt: Make propagate_umount less slow for overlapping mount propagation trees
mnt: In propgate_umount handle visiting mounts in any order
mnt: In umount propagation reparent in a separate pass
Fixes: 4f757f3cbf ("make sure that mntns_install() doesn't end up with referral for root")
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrei Vagin <avagin@openvz.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
While investigating some poor umount performance I realized that in
the case of overlapping mount trees where some of the mounts are locked
the code has been failing to unmount all of the mounts it should
have been unmounting.
This failure to unmount all of the necessary
mounts can be reproduced with:
$ cat locked_mounts_test.sh
mount -t tmpfs test-base /mnt
mount --make-shared /mnt
mkdir -p /mnt/b
mount -t tmpfs test1 /mnt/b
mount --make-shared /mnt/b
mkdir -p /mnt/b/10
mount -t tmpfs test2 /mnt/b/10
mount --make-shared /mnt/b/10
mkdir -p /mnt/b/10/20
mount --rbind /mnt/b /mnt/b/10/20
unshare -Urm --propagation unchaged /bin/sh -c 'sleep 5; if [ $(grep test /proc/self/mountinfo | wc -l) -eq 1 ] ; then echo SUCCESS ; else echo FAILURE ; fi'
sleep 1
umount -l /mnt/b
wait %%
$ unshare -Urm ./locked_mounts_test.sh
This failure is corrected by removing the prepass that marks mounts
that may be umounted.
A first pass is added that umounts mounts if possible and if not sets
mount mark if they could be unmounted if they weren't locked and adds
them to a list to umount possibilities. This first pass reconsiders
the mounts parent if it is on the list of umount possibilities, ensuring
that information of umoutability will pass from child to mount parent.
A second pass then walks through all mounts that are umounted and processes
their children unmounting them or marking them for reparenting.
A last pass cleans up the state on the mounts that could not be umounted
and if applicable reparents them to their first parent that remained
mounted.
While a bit longer than the old code this code is much more robust
as it allows information to flow up from the leaves and down
from the trunk making the order in which mounts are encountered
in the umount propgation tree irrelevant.
Cc: stable@vger.kernel.org
Fixes: 0c56fe3142 ("mnt: Don't propagate unmounts to locked mounts")
Reviewed-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
