Re: [PATCH net v2] ip6mr: fix stale iterator

From: Nikolay Aleksandrov <redacted>
Date: Wed, 31 Jan 2018 16:29:30 +0200

When we dump the ip6mr mfc entries via proc, we initialize an iterator
with the table to dump but we don't clear the cache pointer which might
be initialized from a prior read on the same descriptor that ended. This
can result in lock imbalance (an unnecessary unlock) leading to other
crashes and hangs. Clear the cache pointer like ipmr does to fix the issue.
Thanks for the reliable reproducer.

Here's syzbot's trace:

 ...

Reported-by: syzbot <redacted>
Signed-off-by: Nikolay Aleksandrov <redacted>
---
v2: make sure the trace doesn't ruin the patch
No fixes tag because it seems this has been there forever.

Applied and queued up for -stable.