From: Simon Horman <horms@kernel•org>
To: Sven Eckelmann <sven@narfation•org>
Cc: "David S. Miller" <davem@davemloft•net>,
Eric Dumazet <edumazet@google•com>,
Jakub Kicinski <kuba@kernel•org>, Paolo Abeni <pabeni@redhat•com>,
b.a.t.m.a.n@lists•open-mesh.org, netdev@vger•kernel.org,
stable@vger•kernel.org,
syzbot+f8812454d9b3ac00d282@syzkaller•appspotmail.com
Subject: Re: [PATCH net] batman-adv: Hold rtnl lock during MTU update via netlink
Date: Tue, 22 Aug 2023 09:55:39 +0200 [thread overview]
Message-ID: <20230822075539.GU2711035@kernel.org> (raw)
In-Reply-To: <20230821-batadv-missing-mtu-rtnl-lock-v1-1-1c5a7bfe861e@narfation.org>
On Mon, Aug 21, 2023 at 09:48:48PM +0200, Sven Eckelmann wrote:
> The automatic recalculation of the maximum allowed MTU is usually triggered
> by code sections which are already rtnl lock protected by callers outside
> of batman-adv. But when the fragmentation setting is changed via
> batman-adv's own batadv genl family, then the rtnl lock is not yet taken.
>
> But dev_set_mtu requires that the caller holds the rtnl lock because it
> uses netdevice notifiers. And this code will then fail the check for this
> lock:
>
> RTNL: assertion failed at net/core/dev.c (1953)
>
> Cc: stable@vger•kernel.org
> Reported-by: syzbot+f8812454d9b3ac00d282@syzkaller•appspotmail.com
> Fixes: c6a953cce8d0 ("batman-adv: Trigger events for auto adjusted MTU")
> Signed-off-by: Sven Eckelmann <sven@narfation•org>
Reviewed-by: Simon Horman <horms@kernel•org>
> ---
> This problem was just identified by syzbot [1]. I hope it is ok to directly
> send this patch to netdev instead of creating a single-patch PR from
> the batadv/net branch. If you still prefer a PR then we can also prepare
> it.
>
> [1] https://lore.kernel.org/r/0000000000009bbb4b0603717cde@google.com
...
next prev parent reply other threads:[~2023-08-22 7:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-21 19:48 [PATCH net] batman-adv: Hold rtnl lock during MTU update via netlink Sven Eckelmann
2023-08-22 7:55 ` Simon Horman [this message]
2023-08-23 0:30 ` patchwork-bot+netdevbpf
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