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Uprobes: Fix kernel oops with delayed_uprobe_remove()

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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: 1cc33161a8 ("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>
This commit is contained in:
Ravi Bangoria 2018-12-05 09:04:23 +05:30 committed by Steven Rostedt (VMware)
parent 5cf99a0f31
commit 1aed58e67a
1 changed files with 2 additions and 0 deletions
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2
kernel/events/uprobes.c
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@ -572,7 +572,9 @@ static void put_uprobe(struct uprobe *uprobe)
* gets called, we don't get a chance to remove uprobe from
* delayed_uprobe_list from remove_breakpoint(). Do it here.
*/
mutex_lock(&delayed_uprobe_lock);
delayed_uprobe_remove(uprobe, NULL);
mutex_unlock(&delayed_uprobe_lock);
kfree(uprobe);
}
}