Re: [PATCH net 0/2] wireguard fixes for 5.9-rc5

[David Miller <davem@davemloft.net>]

From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Wed,  9 Sep 2020 13:58:13 +0200

> Yesterday, Eric reported a race condition found by syzbot. This series
> contains two commits, one that fixes the direct issue, and another that
> addresses the more general issue, as a defense in depth.
> 
> 1) The basic problem syzbot unearthed was that one particular mutation
>    of handshake->entry was not protected by the handshake mutex like the
>    other cases, so this patch basically just reorders a line to make
>    sure the mutex is actually taken at the right point. Most of the work
>    here went into making sure the race was fully understood and making a
>    reproducer (which syzbot was unable to do itself, due to the rarity
>    of the race).
> 
> 2) Eric's initial suggestion for fixing this was taking a spinlock
>    around the hash table replace function where the null ptr deref was
>    happening. This doesn't address the main problem in the most precise
>    possible way like (1) does, but it is a good suggestion for
>    defense-in-depth, in case related issues come up in the future, and
>    basically costs nothing from a performance perspective. I thought it
>    aided in implementing a good general rule: all mutators of that hash
>    table take the table lock. So that's part of this series as a
>    companion.
> 
> Both of these contain Fixes: tags and are good candidates for stable.

Series applied and queued up for -stable, thanks.