kernel_optimize_test/kernel
Paul Gortmaker df34f88862 cgroup1: fix leaked context root causing sporadic NULL deref in LTP
commit 1e7107c5ef44431bc1ebbd4c353f1d7c22e5f2ec upstream.

Richard reported sporadic (roughly one in 10 or so) null dereferences and
other strange behaviour for a set of automated LTP tests.  Things like:

   BUG: kernel NULL pointer dereference, address: 0000000000000008
   #PF: supervisor read access in kernel mode
   #PF: error_code(0x0000) - not-present page
   PGD 0 P4D 0
   Oops: 0000 [#1] PREEMPT SMP PTI
   CPU: 0 PID: 1516 Comm: umount Not tainted 5.10.0-yocto-standard #1
   Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-48-gd9c812dda519-prebuilt.qemu.org 04/01/2014
   RIP: 0010:kernfs_sop_show_path+0x1b/0x60

...or these others:

   RIP: 0010:do_mkdirat+0x6a/0xf0
   RIP: 0010:d_alloc_parallel+0x98/0x510
   RIP: 0010:do_readlinkat+0x86/0x120

There were other less common instances of some kind of a general scribble
but the common theme was mount and cgroup and a dubious dentry triggering
the NULL dereference.  I was only able to reproduce it under qemu by
replicating Richard's setup as closely as possible - I never did get it
to happen on bare metal, even while keeping everything else the same.

In commit 71d883c37e ("cgroup_do_mount(): massage calling conventions")
we see this as a part of the overall change:

   --------------
           struct cgroup_subsys *ss;
   -       struct dentry *dentry;

   [...]

   -       dentry = cgroup_do_mount(&cgroup_fs_type, fc->sb_flags, root,
   -                                CGROUP_SUPER_MAGIC, ns);

   [...]

   -       if (percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
   -               struct super_block *sb = dentry->d_sb;
   -               dput(dentry);
   +       ret = cgroup_do_mount(fc, CGROUP_SUPER_MAGIC, ns);
   +       if (!ret && percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
   +               struct super_block *sb = fc->root->d_sb;
   +               dput(fc->root);
                   deactivate_locked_super(sb);
                   msleep(10);
                   return restart_syscall();
           }
   --------------

In changing from the local "*dentry" variable to using fc->root, we now
export/leave that dentry pointer in the file context after doing the dput()
in the unlikely "is_dying" case.   With LTP doing a crazy amount of back to
back mount/unmount [testcases/bin/cgroup_regression_5_1.sh] the unlikely
becomes slightly likely and then bad things happen.

A fix would be to not leave the stale reference in fc->root as follows:

   --------------
                  dput(fc->root);
  +               fc->root = NULL;
                  deactivate_locked_super(sb);
   --------------

...but then we are just open-coding a duplicate of fc_drop_locked() so we
simply use that instead.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: stable@vger.kernel.org      # v5.1+
Reported-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Fixes: 71d883c37e ("cgroup_do_mount(): massage calling conventions")
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-07-31 08:16:11 +02:00
..
bpf bpf: Fix tail_call_reachable rejection for interpreter when jit failed 2021-07-28 14:35:37 +02:00
cgroup cgroup1: fix leaked context root causing sporadic NULL deref in LTP 2021-07-31 08:16:11 +02:00
configs
debug kgdb: fix to kill breakpoints on initmem after boot 2021-03-04 11:38:46 +01:00
dma dma-mapping: handle vmalloc addresses in dma_common_{mmap,get_sgtable} 2021-07-28 14:35:38 +02:00
entry x86/entry: Move nmi entry/exit into common code 2021-03-17 17:06:36 +01:00
events perf: Fix data race between pin_count increment/decrement 2021-06-16 12:01:45 +02:00
gcov gcov: re-fix clang-11+ support 2021-04-14 08:41:58 +02:00
irq genirq/matrix: Prevent allocation counter corruption 2021-05-11 14:47:17 +02:00
kcsan kcsan: Fix debugfs initcall return type 2021-05-26 12:06:54 +02:00
livepatch kernel/: fix repeated words in comments 2020-10-16 11:11:19 -07:00
locking lockdep: Fix wait-type for empty stack 2021-07-14 16:56:10 +02:00
power PM: EM: postpone creating the debugfs dir till fs_initcall 2021-03-30 14:32:04 +02:00
printk printk: fix deadlock when kernel panic 2021-03-04 11:38:41 +01:00
rcu rcu: Reject RCU_LOCKDEP_WARN() false positives 2021-07-20 16:05:38 +02:00
sched sched/fair: Fix CFS bandwidth hrtimer expiry type 2021-07-25 14:36:17 +02:00
time posix-cpu-timers: Fix rearm racing against process tick 2021-07-28 14:35:45 +02:00
trace tracing: Synthetic event field_pos is an index not a boolean 2021-07-28 14:35:45 +02:00
.gitignore kbuild: update config_data.gz only when the content of .config is changed 2021-05-11 14:47:37 +02:00
acct.c kernel: acct.c: fix some kernel-doc nits 2020-10-16 11:11:19 -07:00
async.c
audit_fsnotify.c fsnotify: generalize handle_inode_event() 2020-12-30 11:54:18 +01:00
audit_tree.c fsnotify: generalize handle_inode_event() 2020-12-30 11:54:18 +01:00
audit_watch.c fsnotify: generalize handle_inode_event() 2020-12-30 11:54:18 +01:00
audit.c
audit.h
auditfilter.c
auditsc.c
backtracetest.c
bounds.c
capability.c LSM: Signal to SafeSetID when setting group IDs 2020-10-13 09:17:34 -07:00
compat.c
configs.c
context_tracking.c
cpu_pm.c
cpu.c cpu/hotplug: Cure the cpusets trainwreck 2021-07-19 09:44:59 +02:00
crash_core.c crash_core, vmcoreinfo: append 'SECTION_SIZE_BITS' to vmcoreinfo 2021-06-23 14:42:52 +02:00
crash_dump.c
cred.c cred: add missing return error code when set_cred_ucounts() failed 2021-07-14 16:56:55 +02:00
delayacct.c
dma.c
exec_domain.c
exit.c kernel/io_uring: cancel io_uring before task works 2021-01-30 13:55:18 +01:00
extable.c
fail_function.c fail_function: Remove a redundant mutex unlock 2020-11-19 11:58:16 -08:00
fork.c sched/core: Initialize the idle task with preemption disabled 2021-07-14 16:55:50 +02:00
freezer.c Revert "kernel: freezer should treat PF_IO_WORKER like PF_KTHREAD for freezing" 2021-04-07 15:00:14 +02:00
futex.c mm, futex: fix shared futex pgoff on shmem huge page 2021-06-30 08:47:29 -04:00
gen_kheaders.sh
groups.c LSM: Signal to SafeSetID when setting group IDs 2020-10-13 09:17:34 -07:00
hung_task.c kernel/hung_task.c: make type annotations consistent 2020-11-02 12:14:19 -08:00
iomem.c
irq_work.c
jump_label.c jump_label: Fix jump_label_text_reserved() vs __init 2021-07-20 16:05:58 +02:00
kallsyms.c treewide: Convert macro and uses of __section(foo) to __section("foo") 2020-10-25 14:51:49 -07:00
kcmp.c exec: Transform exec_update_mutex into a rw_semaphore 2021-01-09 13:46:24 +01:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c
kexec_core.c kernel: kexec: remove the lock operation of system_transition_mutex 2021-02-03 23:28:37 +01:00
kexec_elf.c
kexec_file.c kernel: kexec_file: fix error return code of kexec_calculate_store_digests() 2021-05-19 10:13:09 +02:00
kexec_internal.h
kexec.c LSM: Introduce kernel_post_load_data() hook 2020-10-05 13:37:03 +02:00
kheaders.c
kmod.c
kprobes.c kprobes: Fix to delay the kprobes jump optimization 2021-03-04 11:38:35 +01:00
ksysfs.c
kthread.c kthread_worker: fix return value when kthread_mod_delayed_work() races with kthread_cancel_delayed_work_sync() 2021-07-14 16:56:02 +02:00
latencytop.c
Makefile kbuild: update config_data.gz only when the content of .config is changed 2021-05-11 14:47:37 +02:00
module_signature.c module: harden ELF info handling 2021-03-25 09:04:11 +01:00
module_signing.c module: harden ELF info handling 2021-03-25 09:04:11 +01:00
module-internal.h
module.c module: limit enabling module.sig_enforce 2021-06-30 08:47:15 -04:00
notifier.c
nsproxy.c
padata.c
panic.c panic: don't dump stack twice on warn 2020-11-14 11:26:04 -08:00
params.c params: Replace zero-length array with flexible-array member 2020-10-29 17:22:59 -05:00
pid_namespace.c kernel/: fix repeated words in comments 2020-10-16 11:11:19 -07:00
pid.c exec: Transform exec_update_mutex into a rw_semaphore 2021-01-09 13:46:24 +01:00
profile.c
ptrace.c ptrace: make ptrace() fail if the tracee changed its pid unexpectedly 2021-05-26 12:06:49 +02:00
range.c kernel.h: split out min()/max() et al. helpers 2020-10-16 11:11:19 -07:00
reboot.c reboot: fix overflow parsing reboot cpu number 2020-11-14 11:26:03 -08:00
regset.c
relay.c kernel/relay.c: drop unneeded initialization 2020-10-16 11:11:22 -07:00
resource.c kernel/resource: make walk_mem_res() find all busy IORESOURCE_MEM resources 2021-05-19 10:13:09 +02:00
rseq.c
scftorture.c
scs.c
seccomp.c seccomp: Refactor notification handler to prepare for new semantics 2021-06-03 09:00:31 +02:00
signal.c ptrace: fix task_join_group_stop() for the case when current is traced 2020-11-02 12:14:19 -08:00
smp.c smp: Fix smp_call_function_single_async prototype 2021-05-14 09:50:46 +02:00
smpboot.c sched/core: Initialize the idle task with preemption disabled 2021-07-14 16:55:50 +02:00
smpboot.h
softirq.c softirq: Add debug check to __raise_softirq_irqoff() 2020-09-16 15:18:56 +02:00
stackleak.c stackleak: let stack_erasing_sysctl take a kernel pointer buffer 2020-09-19 13:13:39 -07:00
stacktrace.c stacktrace: Remove reliable argument from arch_stack_walk() callback 2020-09-18 14:24:16 +01:00
static_call.c static_call: Fix static_call_text_reserved() vs __init 2021-07-20 16:05:58 +02:00
stop_machine.c stop_machine, rcu: Mark functions as notrace 2020-10-26 12:12:27 +01:00
sys_ni.c mm/madvise: introduce process_madvise() syscall: an external memory hinting API 2020-10-18 09:27:10 -07:00
sys.c Add a reference to ucounts for each cred 2021-07-14 16:55:48 +02:00
sysctl-test.c
sysctl.c sysctl.c: fix underflow value setting risk in vm_table 2021-03-17 17:06:25 +01:00
task_work.c task_work: cleanup notification modes 2020-10-17 15:05:30 -06:00
taskstats.c taskstats: move specifying netlink policy back to ops 2020-10-02 19:11:12 -07:00
test_kprobes.c
torture.c
tracepoint.c tracepoints: Update static_call before tp_funcs when adding a tracepoint 2021-07-28 14:35:45 +02:00
tsacct.c
ucount.c Add a reference to ucounts for each cred 2021-07-14 16:55:48 +02:00
uid16.c
uid16.h
umh.c usermodehelper: reset umask to default before executing user process 2020-10-06 10:31:52 -07:00
up.c smp: Fix smp_call_function_single_async prototype 2021-05-14 09:50:46 +02:00
user_namespace.c Add a reference to ucounts for each cred 2021-07-14 16:55:48 +02:00
user-return-notifier.c
user.c
usermode_driver.c bpf: Fix umd memory leak in copy_process() 2021-03-30 14:32:03 +02:00
utsname_sysctl.c
utsname.c
watch_queue.c
watchdog_hld.c
watchdog.c watchdog: fix barriers when printing backtraces from all CPUs 2021-05-19 10:13:00 +02:00
workqueue_internal.h
workqueue.c workqueue: fix UAF in pwq_unbound_release_workfn() 2021-07-31 08:16:11 +02:00