Hi Dmitry,
On 01/02/2016 01:19 PM, Dmitry Vyukov wrote:
On Sat, Jan 2, 2016 at 12:33 PM, Manfred Spraul
<manfred@xxxxxxxxxxxxxxxx> wrote:
Hi Dmitry,
shm locking differs too much from msg/sem locking, I never looked at it in
depth, so I'm not able to perform a proper review.
Except for the obvious: Races that can be triggered from user space are
inacceptable.
Regardless if there is a BUG_ON, a WARN_ON or nothing at all.
On 12/21/2015 04:44 PM, Dmitry Vyukov wrote:
+
+/* This is called by fork, once for every shm attach. */
+static void shm_open(struct vm_area_struct *vma)
+{
+ int err = __shm_open(vma);
+ /*
+ * We raced in the idr lookup or with shm_destroy().
+ * Either way, the ID is busted.
+ */
+ WARN_ON_ONCE(err);
}
Is it possible to trigger this race? Parallel IPC_RMID & fork()?
Hi Manfred,
As far as I see my reproducer triggers exactly this warning (and later a crash).
Do I understand it right, shm_open() is also called by remap()?
Then please update the comment above shm_open().
And: If this is something that userspace can trigger, why a WARN_ON_ONCE()?
If the WARN_ON doesn't indicate a bug, then I would remove it entirely.
--
Manfred
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