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d574567537
css_task_iter_next() checked @it->cur_task before grabbing
css_set_lock and assumed that the result won't change afterwards;
however, tasks could leave the cgroup being iterated terminating the
iterator before css_task_lock is acquired. If this happens,
css_task_iter_next() tries to calculate the current task from NULL
cg_list pointer leading to the following oops.
BUG: unable to handle kernel paging request at fffffffffffff7d0
IP: [<ffffffff810d5f22>] css_task_iter_next+0x42/0x80
...
CPU: 4 PID: 6391 Comm: JobQDisp2 Not tainted 4.0.9-22_fbk4_rc3_81616_ge8d9cb6 #1
Hardware name: Quanta Freedom/Winterfell, BIOS F03_3B08 03/04/2014
task: ffff880868e46400 ti: ffff88083404c000 task.ti: ffff88083404c000
RIP: 0010:[<ffffffff810d5f22>] [<ffffffff810d5f22>] css_task_iter_next+0x42/0x80
RSP: 0018:ffff88083404fd28 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88083404fd68 RCX: ffff8804697fb8b0
RDX: fffffffffffff7c0 RSI: ffff8803b7dff800 RDI: ffffffff822c0278
RBP: ffff88083404fd38 R08: 0000000000017160 R09: ffff88046f4070c0
R10: ffffffff810d61f7 R11: 0000000000000293 R12: ffff880863bf8400
R13: ffff88046b87fd80 R14: 0000000000000000 R15: ffff88083404fe58
FS: 00007fa0567e2700(0000) GS:ffff88046f900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffffffff7d0 CR3: 0000000469568000 CR4: 00000000001406e0
Stack:
0000000000000246 0000000000000000 ffff88083404fde8 ffffffff810d6248
ffff88083404fd68 0000000000000000 ffff8803b7dff800 000001ef000001ee
0000000000000000 0000000000000000 ffff880863bf8568 0000000000000000
Call Trace:
[<ffffffff810d6248>] cgroup_pidlist_start+0x258/0x550
[<ffffffff810cf66d>] cgroup_seqfile_start+0x1d/0x20
[<ffffffff8121f8ef>] kernfs_seq_start+0x5f/0xa0
[<ffffffff811cab76>] seq_read+0x166/0x380
[<ffffffff812200fd>] kernfs_fop_read+0x11d/0x180
[<ffffffff811a7398>] __vfs_read+0x18/0x50
[<ffffffff811a745d>] vfs_read+0x8d/0x150
[<ffffffff811a756f>] SyS_read+0x4f/0xb0
[<ffffffff818d4772>] system_call_fastpath+0x12/0x17
Fix it by moving the termination condition check inside css_set_lock.
@it->cur_task is now cleared after being put and @it->task_pos is
tested for termination instead of @it->cset_pos as they indicate the
same condition and @it->task_pos is what's being dereferenced.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Calvin Owens <calvinowens@fb.com>
Fixes:
|
||
|---|---|---|
| .. | ||
| bpf | ||
| configs | ||
| debug | ||
| events | ||
| gcov | ||
| irq | ||
| livepatch | ||
| locking | ||
| power | ||
| printk | ||
| rcu | ||
| sched | ||
| time | ||
| trace | ||
| .gitignore | ||
| acct.c | ||
| async.c | ||
| audit_fsnotify.c | ||
| audit_tree.c | ||
| audit_watch.c | ||
| audit.c | ||
| audit.h | ||
| auditfilter.c | ||
| auditsc.c | ||
| backtracetest.c | ||
| bounds.c | ||
| capability.c | ||
| cgroup_freezer.c | ||
| cgroup_pids.c | ||
| cgroup.c | ||
| compat.c | ||
| configs.c | ||
| context_tracking.c | ||
| cpu_pm.c | ||
| cpu.c | ||
| cpuset.c | ||
| crash_dump.c | ||
| cred.c | ||
| delayacct.c | ||
| dma.c | ||
| elfcore.c | ||
| exec_domain.c | ||
| exit.c | ||
| extable.c | ||
| fork.c | ||
| freezer.c | ||
| futex_compat.c | ||
| futex.c | ||
| groups.c | ||
| hung_task.c | ||
| irq_work.c | ||
| jump_label.c | ||
| kallsyms.c | ||
| kcmp.c | ||
| Kconfig.freezer | ||
| Kconfig.hz | ||
| Kconfig.locks | ||
| Kconfig.preempt | ||
| kexec_core.c | ||
| kexec_file.c | ||
| kexec_internal.h | ||
| kexec.c | ||
| kmod.c | ||
| kprobes.c | ||
| ksysfs.c | ||
| kthread.c | ||
| latencytop.c | ||
| Makefile | ||
| membarrier.c | ||
| memremap.c | ||
| module_signing.c | ||
| module-internal.h | ||
| module.c | ||
| notifier.c | ||
| nsproxy.c | ||
| padata.c | ||
| panic.c | ||
| params.c | ||
| pid_namespace.c | ||
| pid.c | ||
| profile.c | ||
| ptrace.c | ||
| range.c | ||
| reboot.c | ||
| relay.c | ||
| resource.c | ||
| seccomp.c | ||
| signal.c | ||
| smp.c | ||
| smpboot.c | ||
| smpboot.h | ||
| softirq.c | ||
| stacktrace.c | ||
| stop_machine.c | ||
| sys_ni.c | ||
| sys.c | ||
| sysctl_binary.c | ||
| sysctl.c | ||
| task_work.c | ||
| taskstats.c | ||
| test_kprobes.c | ||
| torture.c | ||
| tracepoint.c | ||
| tsacct.c | ||
| uid16.c | ||
| up.c | ||
| user_namespace.c | ||
| user-return-notifier.c | ||
| user.c | ||
| utsname_sysctl.c | ||
| utsname.c | ||
| watchdog.c | ||
| workqueue_internal.h | ||
| workqueue.c | ||