Move (most of) the definitions of hashtab_search() and hashtab_insert()
to the header file. In combination with the previous patch, this avoids
calling the callbacks indirectly by function pointers and allows for
better optimization, leading to a drastic performance improvement of
these operations.
With this patch, I measured a speed up in the following areas (measured
on x86_64 F32 VM with 4 CPUs):
1. Policy load (`load_policy`) - takes ~150 ms instead of ~230 ms.
2. `chcon -R unconfined_u:object_r:user_tmp_t:s0:c381,c519 /tmp/linux-src`
where /tmp/linux-src is an extracted linux-5.7 source tarball -
takes ~522 ms instead of ~576 ms. This is because of many
symtab_search() calls in string_to_context_struct() when there are
many categories specified in the context.
3. `stress-ng --msg 1 --msg-ops 10000000` - takes 12.41 s instead of
13.95 s (consumes 18.6 s of kernel CPU time instead of 21.6 s).
This is thanks to security_transition_sid() being ~43% faster after
this patch.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Refactor searching and inserting into hashtabs to pave the way for
converting hashtab_search() and hashtab_insert() to inline functions in
the next patch. This will avoid indirect calls and allow the compiler to
better optimize individual callers, leading to a significant performance
improvement.
In order to avoid the indirect calls, the key hashing and comparison
callbacks need to be extracted from the hashtab struct and passed
directly to hashtab_search()/_insert() by the callers so that the
callback address is always known at compile time. The kernel's
rhashtable library (<linux/rhashtable*.h>) does the same thing.
This of course makes the hashtab functions slightly easier to misuse by
passing a wrong callback set, but unfortunately there is no better way
to implement a hash table that is both generic and efficient in C. This
patch tries to somewhat mitigate this by only calling the hashtab
functions in the same file where the corresponding callbacks are
defined (wrapping them into more specialized functions as needed).
Note that this patch doesn't bring any benefit without also moving the
definitions of hashtab_search() and -_insert() to the header file, which
is done in a follow-up patch for easier review of the hashtab.c changes
in this patch.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This encapsulates symtab a little better and will help with further
refactoring later.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
`sizeof buf` changed to `sizeof(buf)`
Signed-off-by: Ethan Edwards <ethancarteredwards@gmail.com>
[PM: rewrote the subject line]
Signed-off-by: Paul Moore <paul@paul-moore.com>
In general SELinux no longer treats undefined object classes or permissions
in the policy as a fatal error, instead handling them in accordance with
handle_unknown. However, the process class and process transition and
dyntransition permissions are still required to be defined due to
dependencies on these definitions for default labeling behaviors,
role and range transitions in older policy versions that lack an explicit
class field, and role allow checking. Log error messages in these cases
since otherwise the policy load will fail silently with no indication
to the user as to the underlying cause. While here, fix the checking for
process transition / dyntransition so that omitting either permission is
handled as an error; both are needed in order to ensure that role allow
checking is consistently applied.
Reported-by: bauen1 <j2468h@googlemail.com>
Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
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Merge tag 'selinux-pr-20200601' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux
Pull SELinux updates from Paul Moore:
"The highlights:
- A number of improvements to various SELinux internal data
structures to help improve performance. We move the role
transitions into a hash table. In the content structure we shift
from hashing the content string (aka SELinux label) to the
structure itself, when it is valid. This last change not only
offers a speedup, but it helps us simplify the code some as well.
- Add a new SELinux policy version which allows for a more space
efficient way of storing the filename transitions in the binary
policy. Given the default Fedora SELinux policy with the unconfined
module enabled, this change drops the policy size from ~7.6MB to
~3.3MB. The kernel policy load time dropped as well.
- Some fixes to the error handling code in the policy parser to
properly return error codes when things go wrong"
* tag 'selinux-pr-20200601' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
selinux: netlabel: Remove unused inline function
selinux: do not allocate hashtabs dynamically
selinux: fix return value on error in policydb_read()
selinux: simplify range_write()
selinux: fix error return code in policydb_read()
selinux: don't produce incorrect filename_trans_count
selinux: implement new format of filename transitions
selinux: move context hashing under sidtab
selinux: hash context structure directly
selinux: store role transitions in a hash table
selinux: drop unnecessary smp_load_acquire() call
selinux: fix warning Comparison to bool
It is simpler to allocate them statically in the corresponding
structure, avoiding unnecessary kmalloc() calls and pointer
dereferencing.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
[PM: manual merging required in policydb.c]
Signed-off-by: Paul Moore <paul@paul-moore.com>
The value of rc is still zero from the last assignment when the error
path is taken. Fix it by setting it to -ENOMEM before the
hashtab_create() call.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: e67b2ec9f6 ("selinux: store role transitions in a hash table")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
No need to traverse the hashtab to count its elements, hashtab already
tracks it for us.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Fix to return negative error code -ENOMEM from the kvcalloc() error
handling case instead of 0, as done elsewhere in this function.
Fixes: acdf52d97f ("selinux: convert to kvmalloc")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
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Merge tag 'selinux-pr-20200430' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux
Pull SELinux fixes from Paul Moore:
"Two more SELinux patches to fix problems in the v5.7-rcX releases.
Wei Yongjun's patch fixes a return code in an error path, and my patch
fixes a problem where we were not correctly applying access controls
to all of the netlink messages in the netlink_send LSM hook"
* tag 'selinux-pr-20200430' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
selinux: properly handle multiple messages in selinux_netlink_send()
selinux: fix error return code in cond_read_list()
Fix to return negative error code -ENOMEM from the error handling
case instead of 0, as done elsewhere in this function.
Fixes: 60abd3181d ("selinux: convert cond_list to array")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
I thought I fixed the counting in filename_trans_read_helper() to count
the compat rule count correctly in the final version, but it's still
wrong. To really count the same thing as in the compat path, we'd need
to add up the cardinalities of stype bitmaps of all datums.
Since the kernel currently doesn't implement an ebitmap_cardinality()
function (and computing the proper count would just waste CPU cycles
anyway), just document that we use the field only in case of the old
format and stop updating it in filename_trans_read_helper().
Fixes: 4300590243 ("selinux: implement new format of filename transitions")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Implement a new, more space-efficient way of storing filename
transitions in the binary policy. The internal structures have already
been converted to this new representation; this patch just implements
reading/writing an equivalent represntation from/to the binary policy.
This new format reduces the size of Fedora policy from 7.6 MB to only
3.3 MB (with policy optimization enabled in both cases). With the
unconfined module disabled, the size is reduced from 3.3 MB to 2.4 MB.
The time to load policy into kernel is also shorter with the new format.
On Fedora Rawhide x86_64 it dropped from 157 ms to 106 ms; without the
unconfined module from 115 ms to 105 ms.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Now that context hash computation no longer depends on policydb, we can
simplify things by moving the context hashing completely under sidtab.
The hash is still cached in sidtab entries, but not for the in-flight
context structures.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Always hashing the string representation is inefficient. Just hash the
contents of the structure directly (using jhash). If the context is
invalid (str & len are set), then hash the string as before, otherwise
hash the structured data.
Since the context hashing function is now faster (about 10 times), this
patch decreases the overhead of security_transition_sid(), which is
called from many hooks.
The jhash function seemed as a good choice, since it is used as the
default hashing algorithm in rhashtable.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Jeff Vander Stoep <jeffv@google.com>
Tested-by: Jeff Vander Stoep <jeffv@google.com>
[PM: fixed some spelling errors in the comments pointed out by JVS]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Currently, they are stored in a linked list, which adds significant
overhead to security_transition_sid(). On Fedora, with 428 role
transitions in policy, converting this list to a hash table cuts down
its run time by about 50%. This was measured by running 'stress-ng --msg
1 --msg-ops 100000' under perf with and without this patch.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
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Merge tag 'selinux-pr-20200416' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux
Pull SELinux fix from Paul Moore:
"One small SELinux fix to ensure we cleanup properly on an error
condition"
* tag 'selinux-pr-20200416' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
selinux: free str on error in str_read()
In commit 66f8e2f03c ("selinux: sidtab reverse lookup hash table") the
corresponding load is moved under the spin lock, so there is no race
possible and we can read the count directly. The smp_store_release() is
still needed to avoid racing with the lock-free readers.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
In [see "Fixes:"] I missed the fact that str_read() may give back an
allocated pointer even if it returns an error, causing a potential
memory leak in filename_trans_read_one(). Fix this by making the
function free the allocated string whenever it returns a non-zero value,
which also makes its behavior more obvious and prevents repeating the
same mistake in the future.
Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Addresses-Coverity-ID: 1461665 ("Resource leaks")
Fixes: c3a276111e ("selinux: optimize storage of filename transitions")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>
fix below warnings reported by coccicheck
security/selinux/ss/mls.c:539:39-43: WARNING: Comparison to bool
security/selinux/ss/services.c:1815:46-50: WARNING: Comparison to bool
security/selinux/ss/services.c:1827:46-50: WARNING: Comparison to bool
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
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Merge tag 'selinux-pr-20200330' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux
Pull SELinux updates from Paul Moore:
"We've got twenty SELinux patches for the v5.7 merge window, the
highlights are below:
- Deprecate setting /sys/fs/selinux/checkreqprot to 1.
This flag was originally created to deal with legacy userspace and
the READ_IMPLIES_EXEC personality flag. We changed the default from
1 to 0 back in Linux v4.4 and now we are taking the next step of
deprecating it, at some point in the future we will take the final
step of rejecting 1.
- Allow kernfs symlinks to inherit the SELinux label of the parent
directory. In order to preserve backwards compatibility this is
protected by the genfs_seclabel_symlinks SELinux policy capability.
- Optimize how we store filename transitions in the kernel, resulting
in some significant improvements to policy load times.
- Do a better job calculating our internal hash table sizes which
resulted in additional policy load improvements and likely general
SELinux performance improvements as well.
- Remove the unused initial SIDs (labels) and improve how we handle
initial SIDs.
- Enable per-file labeling for the bpf filesystem.
- Ensure that we properly label NFS v4.2 filesystems to avoid a
temporary unlabeled condition.
- Add some missing XFS quota command types to the SELinux quota
access controls.
- Fix a problem where we were not updating the seq_file position
index correctly in selinuxfs.
- We consolidate some duplicated code into helper functions.
- A number of list to array conversions.
- Update Stephen Smalley's email address in MAINTAINERS"
* tag 'selinux-pr-20200330' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
selinux: clean up indentation issue with assignment statement
NFS: Ensure security label is set for root inode
MAINTAINERS: Update my email address
selinux: avtab_init() and cond_policydb_init() return void
selinux: clean up error path in policydb_init()
selinux: remove unused initial SIDs and improve handling
selinux: reduce the use of hard-coded hash sizes
selinux: Add xfs quota command types
selinux: optimize storage of filename transitions
selinux: factor out loop body from filename_trans_read()
security: selinux: allow per-file labeling for bpffs
selinux: generalize evaluate_cond_node()
selinux: convert cond_expr to array
selinux: convert cond_av_list to array
selinux: convert cond_list to array
selinux: sel_avc_get_stat_idx should increase position index
selinux: allow kernfs symlinks to inherit parent directory context
selinux: simplify evaluate_cond_node()
Documentation,selinux: deprecate setting checkreqprot to 1
selinux: move status variables out of selinux_ss
The assignment of e->type_names is indented one level too deep,
clean this up by removing the extraneous tab.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
The avtab_init() and cond_policydb_init() functions always return
zero so mark them as returning void and update the callers not to
check for a return value.
Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Commit e0ac568de1 ("selinux: reduce the use of hard-coded hash sizes")
moved symtab initialization out of policydb_init(), but left the cleanup
of symtabs from the error path. This patch fixes the oversight.
Suggested-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae6 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596eafdd ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
8677ce5e8f
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: https://github.com/SELinuxProject/selinux-kernel/issues/12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Instead allocate hash tables with just the right size based on the
actual number of elements (which is almost always known beforehand, we
just need to defer the hashtab allocation to the right time). The only
case when we don't know the size (with the current policy format) is the
new filename transitions hashtable. Here I just left the existing value.
After this patch, the time to load Fedora policy on x86_64 decreases
from 790 ms to 167 ms. If the unconfined module is removed, it decreases
from 750 ms to 122 ms. It is also likely that other operations are going
to be faster, mainly string_to_context_struct() or mls_compute_sid(),
but I didn't try to quantify that.
The memory usage of all hash table arrays increases from ~58 KB to
~163 KB (with Fedora policy on x86_64).
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
In these rules, each rule with the same (target type, target class,
filename) values is (in practice) always mapped to the same result type.
Therefore, it is much more efficient to group the rules by (ttype,
tclass, filename).
Thus, this patch drops the stype field from the key and changes the
datum to be a linked list of one or more structures that contain a
result type and an ebitmap of source types that map the given target to
the given result type under the given filename. The size of the hash
table is also incremented to 2048 to be more optimal for Fedora policy
(which currently has ~2500 unique (ttype, tclass, filename) tuples,
regardless of whether the 'unconfined' module is enabled).
Not only does this dramtically reduce memory usage when the policy
contains a lot of unconfined domains (ergo a lot of filename based
transitions), but it also slightly reduces memory usage of strongly
confined policies (modeled on Fedora policy with 'unconfined' module
disabled) and significantly reduces lookup times of these rules on
Fedora (roughly matches the performance of the rhashtable conversion
patch [1] posted recently to selinux@vger.kernel.org).
An obvious next step is to change binary policy format to match this
layout, so that disk space is also saved. However, since that requires
more work (including matching userspace changes) and this patch is
already beneficial on its own, I'm posting it separately.
Performance/memory usage comparison:
Kernel | Policy load | Policy load | Mem usage | Mem usage | openbench
| | (-unconfined) | | (-unconfined) | (createfiles)
-----------------|-------------|---------------|-----------|---------------|--------------
reference | 1,30s | 0,91s | 90MB | 77MB | 55 us/file
rhashtable patch | 0.98s | 0,85s | 85MB | 75MB | 38 us/file
this patch | 0,95s | 0,87s | 75MB | 75MB | 40 us/file
(Memory usage is measured after boot. With SELinux disabled the memory
usage was ~60MB on the same system.)
[1] https://lore.kernel.org/selinux/20200116213937.77795-1-dev@lynxeye.de/T/
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
It simplifies cleanup in the error path. This will be extra useful in
later patch.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Both callers iterate the cond_list and call it for each node - turn it
into evaluate_cond_nodes(), which does the iteration for them.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Since it is fixed-size after allocation and we know the size beforehand,
using a plain old array is simpler and more efficient.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Since it is fixed-size after allocation and we know the size beforehand,
using a plain old array is simpler and more efficient.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Since it is fixed-size after allocation and we know the size beforehand,
using a plain old array is simpler and more efficient.
While there, also fix signedness of some related variables/parameters.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Currently symlinks on kernel filesystems, like sysfs, are labeled on
creation with the parent filesystem root sid.
Allow symlinks to inherit the parent directory context, so fine-grained
kernfs labeling can be applied to symlinks too and checking contexts
doesn't complain about them.
For backward-compatibility this behavior is contained in a new policy
capability: genfs_seclabel_symlinks
Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
It never fails, so it can just return void.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
It fits more naturally in selinux_state, since it reflects also global
state (the enforcing and policyload fields).
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Avoiding taking a lock in an IRQ context is not enough to prevent
deadlocks, as discovered by syzbot:
===
WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
5.5.0-syzkaller #0 Not tainted
-----------------------------------------------------
syz-executor.0/8927 [HC0[0]:SC0[2]:HE1:SE0] is trying to acquire:
ffff888027c94098 (&(&s->cache_lock)->rlock){+.+.}, at: spin_lock include/linux/spinlock.h:338 [inline]
ffff888027c94098 (&(&s->cache_lock)->rlock){+.+.}, at: sidtab_sid2str_put.part.0+0x36/0x880 security/selinux/ss/sidtab.c:533
and this task is already holding:
ffffffff898639b0 (&(&nf_conntrack_locks[i])->rlock){+.-.}, at: spin_lock include/linux/spinlock.h:338 [inline]
ffffffff898639b0 (&(&nf_conntrack_locks[i])->rlock){+.-.}, at: nf_conntrack_lock+0x17/0x70 net/netfilter/nf_conntrack_core.c:91
which would create a new lock dependency:
(&(&nf_conntrack_locks[i])->rlock){+.-.} -> (&(&s->cache_lock)->rlock){+.+.}
but this new dependency connects a SOFTIRQ-irq-safe lock:
(&(&nf_conntrack_locks[i])->rlock){+.-.}
[...]
other info that might help us debug this:
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&(&s->cache_lock)->rlock);
local_irq_disable();
lock(&(&nf_conntrack_locks[i])->rlock);
lock(&(&s->cache_lock)->rlock);
<Interrupt>
lock(&(&nf_conntrack_locks[i])->rlock);
*** DEADLOCK ***
[...]
===
Fix this by simply locking with irqsave/irqrestore and stop giving up on
!in_task(). It makes the locking a bit slower, but it shouldn't make a
big difference in real workloads. Under the scenario from [1] (only
cache hits) it only increased the runtime overhead from the
security_secid_to_secctx() function from ~2% to ~3% (it was ~5-65%
before introducing the cache).
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1733259
Fixes: d97bd23c2d ("selinux: cache the SID -> context string translation")
Reported-by: syzbot+61cba5033e2072d61806@syzkaller.appspotmail.com
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
In security_load_policy(), we can defer allocating the newpolicydb
ancillary array to after checking state->initialized, thereby avoiding
the pointless allocation when loading policy the first time.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
[PM: merged portions by hand]
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Two places used u32 where there should have been __le32.
Fixes sparse warnings:
CHECK [...]/security/selinux/ss/services.c
[...]/security/selinux/ss/policydb.c:2669:16: warning: incorrect type in assignment (different base types)
[...]/security/selinux/ss/policydb.c:2669:16: expected unsigned int
[...]/security/selinux/ss/policydb.c:2669:16: got restricted __le32 [usertype]
[...]/security/selinux/ss/policydb.c:2674:24: warning: incorrect type in assignment (different base types)
[...]/security/selinux/ss/policydb.c:2674:24: expected unsigned int
[...]/security/selinux/ss/policydb.c:2674:24: got restricted __le32 [usertype]
[...]/security/selinux/ss/policydb.c:2675:24: warning: incorrect type in assignment (different base types)
[...]/security/selinux/ss/policydb.c:2675:24: expected unsigned int
[...]/security/selinux/ss/policydb.c:2675:24: got restricted __le32 [usertype]
[...]/security/selinux/ss/policydb.c:2676:24: warning: incorrect type in assignment (different base types)
[...]/security/selinux/ss/policydb.c:2676:24: expected unsigned int
[...]/security/selinux/ss/policydb.c:2676:24: got restricted __le32 [usertype]
[...]/security/selinux/ss/policydb.c:2681:32: warning: incorrect type in assignment (different base types)
[...]/security/selinux/ss/policydb.c:2681:32: expected unsigned int
[...]/security/selinux/ss/policydb.c:2681:32: got restricted __le32 [usertype]
[...]/security/selinux/ss/policydb.c:2701:16: warning: incorrect type in assignment (different base types)
[...]/security/selinux/ss/policydb.c:2701:16: expected unsigned int
[...]/security/selinux/ss/policydb.c:2701:16: got restricted __le32 [usertype]
[...]/security/selinux/ss/policydb.c:2706:24: warning: incorrect type in assignment (different base types)
[...]/security/selinux/ss/policydb.c:2706:24: expected unsigned int
[...]/security/selinux/ss/policydb.c:2706:24: got restricted __le32 [usertype]
[...]/security/selinux/ss/policydb.c:2707:24: warning: incorrect type in assignment (different base types)
[...]/security/selinux/ss/policydb.c:2707:24: expected unsigned int
[...]/security/selinux/ss/policydb.c:2707:24: got restricted __le32 [usertype]
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
The disabled/enforcing/initialized flags are all accessed concurrently
by threads so use the appropriate accessors that ensure atomicity and
document that it is expected.
Use smp_load/acquire...() helpers (with memory barriers) for the
initialized flag, since it gates access to the rest of the state
structures.
Note that the disabled flag is currently not used for anything other
than avoiding double disable, but it will be used for bailing out of
hooks once security_delete_hooks() is removed.
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
security/selinux/ss/services.c: In function security_port_sid:
security/selinux/ss/services.c:2346:17: warning: variable sidtab set but not used [-Wunused-but-set-variable]
security/selinux/ss/services.c: In function security_ib_endport_sid:
security/selinux/ss/services.c:2435:17: warning: variable sidtab set but not used [-Wunused-but-set-variable]
security/selinux/ss/services.c: In function security_netif_sid:
security/selinux/ss/services.c:2480:17: warning: variable sidtab set but not used [-Wunused-but-set-variable]
security/selinux/ss/services.c: In function security_fs_use:
security/selinux/ss/services.c:2831:17: warning: variable sidtab set but not used [-Wunused-but-set-variable]
Since commit 66f8e2f03c ("selinux: sidtab reverse lookup hash table")
'sidtab' is not used any more, so remove it.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Check to make sure we have loaded a policy before we query the
sidtab's hash stats. Failure to do so could result in a kernel
panic/oops due to a dereferenced NULL pointer.
Fixes: 66f8e2f03c ("selinux: sidtab reverse lookup hash table")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Randomize the layout of key selinux data structures.
Initially this is applied to the selinux_state, selinux_ss,
policydb, and task_security_struct data structures.
NB To test/use this mechanism, one must install the
necessary build-time dependencies, e.g. gcc-plugin-devel on Fedora,
and enable CONFIG_GCC_PLUGIN_RANDSTRUCT in the kernel configuration.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Reviewed-by: Kees Cook <keescook@chromium.org>
[PM: double semi-colon fixed]
Signed-off-by: Paul Moore <paul@paul-moore.com>
Translating a context struct to string can be quite slow, especially if
the context has a lot of category bits set. This can cause quite
noticeable performance impact in situations where the translation needs
to be done repeatedly. A common example is a UNIX datagram socket with
the SO_PASSSEC option enabled, which is used e.g. by systemd-journald
when receiving log messages via datagram socket. This scenario can be
reproduced with:
cat /dev/urandom | base64 | logger &
timeout 30s perf record -p $(pidof systemd-journald) -a -g
kill %1
perf report -g none --pretty raw | grep security_secid_to_secctx
Before the caching introduced by this patch, computing the context
string (security_secid_to_secctx() function) takes up ~65% of
systemd-journald's CPU time (assuming a context with 1024 categories
set and Fedora x86_64 release kernel configs). After this patch
(assuming near-perfect cache hit ratio) this overhead is reduced to just
~2%.
This patch addresses the issue by caching a certain number (compile-time
configurable) of recently used context strings to speed up repeated
translations of the same context, while using only a small amount of
memory.
The cache is integrated into the existing sidtab table by adding a field
to each entry, which when not NULL contains an RCU-protected pointer to
a cache entry containing the cached string. The cache entries are kept
in a linked list sorted according to how recently they were used. On a
cache miss when the cache is full, the least recently used entry is
removed to make space for the new entry.
The patch migrates security_sid_to_context_core() to use the cache (also
a few other functions where it was possible without too much fuss, but
these mostly use the translation for logging in case of error, which is
rare).
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1733259
Cc: Michal Sekletar <msekleta@redhat.com>
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Tested-by: Stephen Smalley <sds@tycho.nsa.gov>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
[PM: lots of merge fixups due to collisions with other sidtab patches]
Signed-off-by: Paul Moore <paul@paul-moore.com>
This replaces the reverse table lookup and reverse cache with a
hashtable which improves cache-miss reverse-lookup times from
O(n) to O(1)* and maintains the same performance as a reverse
cache hit.
This reduces the time needed to add a new sidtab entry from ~500us
to 5us on a Pixel 3 when there are ~10,000 sidtab entries.
The implementation uses the kernel's generic hashtable API,
It uses the context's string represtation as the hash source,
and the kernels generic string hashing algorithm full_name_hash()
to reduce the string to a 32 bit value.
This change also maintains the improvement introduced in
commit ee1a84fdfe ("selinux: overhaul sidtab to fix bug and improve
performance") which removed the need to keep the current sidtab
locked during policy reload. It does however introduce periodic
locking of the target sidtab while converting the hashtable. Sidtab
entries are never modified or removed, so the context struct stored
in the sid_to_context tree can also be used for the context_to_sid
hashtable to reduce memory usage.
This bug was reported by:
- On the selinux bug tracker.
BUG: kernel softlockup due to too many SIDs/contexts #37https://github.com/SELinuxProject/selinux-kernel/issues/37
- Jovana Knezevic on Android's bugtracker.
Bug: 140252993
"During multi-user performance testing, we create and remove users
many times. selinux_android_restorecon_pkgdir goes from 1ms to over
20ms after about 200 user creations and removals. Accumulated over
~280 packages, that adds a significant time to user creation,
making perf benchmarks unreliable."
* Hashtable lookup is only O(1) when n < the number of buckets.
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Reported-by: Stephen Smalley <sds@tycho.nsa.gov>
Reported-by: Jovana Knezevic <jovanak@google.com>
Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>
Tested-by: Stephen Smalley <sds@tycho.nsa.gov>
[PM: subj tweak, removed changelog from patch description]
Signed-off-by: Paul Moore <paul@paul-moore.com>
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Merge tag 'selinux-pr-20191126' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux
Pull selinux updates from Paul Moore:
"Only three SELinux patches for v5.5:
- Remove the size limit on SELinux policies, the limitation was a
lingering vestige and no longer necessary.
- Allow file labeling before the policy is loaded. This should ease
some of the burden when the policy is initially loaded (no need to
relabel files), but it should also help enable some new system
concepts which dynamically create the root filesystem in the
initrd.
- Add support for the "greatest lower bound" policy construct which
is defined as the intersection of the MLS range of two SELinux
labels"
* tag 'selinux-pr-20191126' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
selinux: default_range glblub implementation
selinux: allow labeling before policy is loaded
selinux: remove load size limit
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Merge tag 'selinux-pr-20191007' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux
Pull selinuxfix from Paul Moore:
"One patch to ensure we don't copy bad memory up into userspace"
* tag 'selinux-pr-20191007' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
selinux: fix context string corruption in convert_context()
A policy developer can now specify glblub as a default_range default and
the computed transition will be the intersection of the mls range of
the two contexts.
The glb (greatest lower bound) lub (lowest upper bound) of a range is calculated
as the greater of the low sensitivities and the lower of the high sensitivities
and the and of each category bitmap.
This can be used by MLS solution developers to compute a context that satisfies,
for example, the range of a network interface and the range of a user logging in.
Some examples are:
User Permitted Range | Network Device Label | Computed Label
---------------------|----------------------|----------------
s0-s1:c0.c12 | s0 | s0
s0-s1:c0.c12 | s0-s1:c0.c1023 | s0-s1:c0.c12
s0-s4:c0.c512 | s1-s1:c0.c1023 | s1-s1:c0.c512
s0-s15:c0,c2 | s4-s6:c0.c128 | s4-s6:c0,c2
s0-s4 | s2-s6 | s2-s4
s0-s4 | s5-s8 | INVALID
s5-s8 | s0-s4 | INVALID
Signed-off-by: Joshua Brindle <joshua.brindle@crunchydata.com>
[PM: subject lines and checkpatch.pl fixes]
Signed-off-by: Paul Moore <paul@paul-moore.com>
string_to_context_struct() may garble the context string, so we need to
copy back the contents again from the old context struct to avoid
storing the corrupted context.
Since string_to_context_struct() tokenizes (and therefore truncates) the
context string and we are later potentially copying it with kstrdup(),
this may eventually cause pieces of uninitialized kernel memory to be
disclosed to userspace (when copying to userspace based on the stored
length and not the null character).
How to reproduce on Fedora and similar:
# dnf install -y memcached
# systemctl start memcached
# semodule -d memcached
# load_policy
# load_policy
# systemctl stop memcached
# ausearch -m AVC
type=AVC msg=audit(1570090572.648:313): avc: denied { signal } for pid=1 comm="systemd" scontext=system_u:system_r:init_t:s0 tcontext=system_u:object_r:unlabeled_t:s0 tclass=process permissive=0 trawcon=73797374656D5F75007400000000000070BE6E847296FFFF726F6D000096FFFF76
Cc: stable@vger.kernel.org
Reported-by: Milos Malik <mmalik@redhat.com>
Fixes: ee1a84fdfe ("selinux: overhaul sidtab to fix bug and improve performance")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
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Merge tag 'selinux-pr-20190917' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux
Pull selinux updates from Paul Moore:
- Add LSM hooks, and SELinux access control hooks, for dnotify,
fanotify, and inotify watches. This has been discussed with both the
LSM and fs/notify folks and everybody is good with these new hooks.
- The LSM stacking changes missed a few calls to current_security() in
the SELinux code; we fix those and remove current_security() for
good.
- Improve our network object labeling cache so that we always return
the object's label, even when under memory pressure. Previously we
would return an error if we couldn't allocate a new cache entry, now
we always return the label even if we can't create a new cache entry
for it.
- Convert the sidtab atomic_t counter to a normal u32 with
READ/WRITE_ONCE() and memory barrier protection.
- A few patches to policydb.c to clean things up (remove forward
declarations, long lines, bad variable names, etc)
* tag 'selinux-pr-20190917' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
lsm: remove current_security()
selinux: fix residual uses of current_security() for the SELinux blob
selinux: avoid atomic_t usage in sidtab
fanotify, inotify, dnotify, security: add security hook for fs notifications
selinux: always return a secid from the network caches if we find one
selinux: policydb - rename type_val_to_struct_array
selinux: policydb - fix some checkpatch.pl warnings
selinux: shuffle around policydb.c to get rid of forward declarations
