Re: [PATCH v2] ipv6: addrconf: Fix recursive spin lock call

From: subashab@codeaurora.org
Date: Tue, 2 Feb 2016 02:11:10 -0000

A rcu stall with the following backtrace was seen on a system with
forwarding, optimistic_dad and use_optimistic set. To reproduce,
set these flags and allow ipv6 autoconf.

This occurs because the device write_lock is acquired while already
holding the read_lock. Back trace below -

 ...

v2: do addrconf_dad_kick inside read lock and then acquire write
lock for ipv6_ifa_notify as suggested by Eric

Fixes: 7fd2561e4ebdd ("net: ipv6: Add a sysctl to make optimistic
addresses useful candidates")

Cc: Eric Dumazet <edumazet@google.com>
Cc: Erik Kline <redacted>
Cc: Hannes Frederic Sowa <redacted>
Signed-off-by: Subash Abhinov Kasiviswanathan <redacted>

Applied and queued up for -stable, thanks.