Re: [PATCH net v3] ipv4: Fix use-after-free when flushing FIB tables

[David Miller <davem@davemloft.net>]

From: Ido Schimmel <idosch@mellanox.com>
Date: Wed, 20 Dec 2017 19:34:19 +0200

> Since commit 0ddcf43d5d4a ("ipv4: FIB Local/MAIN table collapse") the
> local table uses the same trie allocated for the main table when custom
> rules are not in use.
> 
> When a net namespace is dismantled, the main table is flushed and freed
> (via an RCU callback) before the local table. In case the callback is
> invoked before the local table is iterated, a use-after-free can occur.
> 
> Fix this by iterating over the FIB tables in reverse order, so that the
> main table is always freed after the local table.
> 
> v3: Reworded comment according to Alex's suggestion.
> v2: Add a comment to make the fix more explicit per Dave's and Alex's
> feedback.
> 
> Fixes: 0ddcf43d5d4a ("ipv4: FIB Local/MAIN table collapse")
> Signed-off-by: Ido Schimmel <idosch@mellanox.com>
> Reported-by: Fengguang Wu <fengguang.wu@intel.com>

Applied and queued up for -stable.