Currently utask->depth is simply the number of allocated/pending
return_instance's in uprobe_task->return_instances list.

handle_trampoline() should decrement this counter every time we
handle/free an instance, but due to typo it does this only if
->chained == T. This means that in the likely case this counter
is never decremented and the probed task can't report more than
MAX_URETPROBE_DEPTH events.

Cc: sta...@vger.kernel.org
Signed-off-by: Oleg Nesterov <o...@redhat.com>
Reported-by: Mikhail Kulemin <mikhail.kule...@ru.ibm.com>
Reported-by: Hemant Kumar Shaw <hks...@linux.vnet.ibm.com>
---
 kernel/events/uprobes.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index f356974..ad8e1bd 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1682,12 +1682,10 @@ static bool handle_trampoline(struct pt_regs *regs)
                tmp = ri;
                ri = ri->next;
                kfree(tmp);
+               utask->depth--;
 
                if (!chained)
                        break;
-
-               utask->depth--;
-
                BUG_ON(!ri);
        }
 
-- 
1.5.5.1


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