netdev - Re: [PATCH net v2 1/3] net: ipv6: fix dst ref loops on input in rpl and seg6 lwtunnels

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Message-ID: <Z63lQiyiNoQkgJFk@shredder>
Date: Thu, 13 Feb 2025 14:27:46 +0200
From: Ido Schimmel <idosch@...sch.org>
To: Justin Iurman <justin.iurman@...ege.be>
Cc: netdev@...r.kernel.org, davem@...emloft.net, dsahern@...nel.org,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	horms@...nel.org, Alexander Aring <alex.aring@...il.com>,
	David Lebrun <dlebrun@...gle.com>
Subject: Re: [PATCH net v2 1/3] net: ipv6: fix dst ref loops on input in rpl
 and seg6 lwtunnels

On Tue, Feb 11, 2025 at 11:16:22PM +0100, Justin Iurman wrote:
> As a follow up to commit 92191dd10730 ("net: ipv6: fix dst ref loops in
> rpl, seg6 and ioam6 lwtunnels"), we also need a conditional dst cache on
> input for seg6_iptunnel and rpl_iptunnel to prevent dst ref loops (i.e.,
> if the packet destination did not change, we may end up recording a
> reference to the lwtunnel in its own cache, and the lwtunnel state will
> never be freed).
> 
> Fixes: a7a29f9c361f ("net: ipv6: add rpl sr tunnel")
> Fixes: af4a2209b134 ("ipv6: sr: use dst_cache in seg6_input")
> Signed-off-by: Justin Iurman <justin.iurman@...ege.be>
> Cc: Alexander Aring <alex.aring@...il.com>
> Cc: David Lebrun <dlebrun@...gle.com>

Not an expert but was asked to take a look. Seems consistent with the
output path and comparing the state address seems safe as it is only
compared and never dereferenced after dropping the dst in the input
path.

I would have probably split it into two patches to make it a bit easier
to backport. 5.4.y needs the seg6 fix, but not the rpl one.

Reviewed-by: Ido Schimmel <idosch@...dia.com>