Re: [GIT PULL] Uprobes: Fix kernel oops with delayed_uprobe_remove()

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 6 Dec 2018 12:47:19 -0500 Steven Rostedt <rostedt@goodmis.org> wrote:

> 
>     Uprobes: Fix kernel oops with delayed_uprobe_remove()
>     
>     There could be a race between task exit and probe unregister:
>     
>       exit_mm()
>       mmput()
>       __mmput()                     uprobe_unregister()
>       uprobe_clear_state()          put_uprobe()
>       delayed_uprobe_remove()       delayed_uprobe_remove()
>     
>     put_uprobe() is calling delayed_uprobe_remove() without taking
>     delayed_uprobe_lock and thus the race sometimes results in a
>     kernel crash. Fix this by taking delayed_uprobe_lock before
>     calling delayed_uprobe_remove() from put_uprobe().
>     
>     Detailed crash log can be found at:
>       Link: http://lkml.kernel.org/r/000000000000140c370577db5ece@google.com
>     
>     Link: http://lkml.kernel.org/r/20181205033423.26242-1-ravi.bangoria@linux.ibm.com
>     
>     Acked-by: Oleg Nesterov <oleg@redhat.com>
>     Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
>     Reported-by: syzbot+cb1fb754b771caca0a88@syzkaller.appspotmail.com
>     Fixes: 1cc33161a83d ("uprobes: Support SDT markers having reference count (semaphore)")
>     Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
>     Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> 

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