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: https://lkml.org/lkml/2018/11/1/1244 Reported-by: syzbot+cb1fb754b771caca0...@syzkaller.appspotmail.com Fixes: 1cc33161a83d ("uprobes: Support SDT markers having reference count (semaphore)") Signed-off-by: Ravi Bangoria <ravi.bango...@linux.ibm.com> --- kernel/events/uprobes.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 322e97bbb437..abbd8da9ac21 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -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); } } -- 2.19.2
