* [PATCH net] batman-adv: Hold rtnl lock during MTU update via netlink
@ 2023-08-21 19:48 Sven Eckelmann
2023-08-22 7:55 ` Simon Horman
2023-08-23 0:30 ` patchwork-bot+netdevbpf
0 siblings, 2 replies; 3+ messages in thread
From: Sven Eckelmann @ 2023-08-21 19:48 UTC (permalink / raw)
To: David S. Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni
Cc: b.a.t.m.a.n, netdev, stable, syzbot+f8812454d9b3ac00d282,
Sven Eckelmann
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>
---
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
---
net/batman-adv/netlink.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/batman-adv/netlink.c b/net/batman-adv/netlink.c
index ad5714f737be..6efbc9275aec 100644
--- a/net/batman-adv/netlink.c
+++ b/net/batman-adv/netlink.c
@@ -495,7 +495,10 @@ static int batadv_netlink_set_mesh(struct sk_buff *skb, struct genl_info *info)
attr = info->attrs[BATADV_ATTR_FRAGMENTATION_ENABLED];
atomic_set(&bat_priv->fragmentation, !!nla_get_u8(attr));
+
+ rtnl_lock();
batadv_update_min_mtu(bat_priv->soft_iface);
+ rtnl_unlock();
}
if (info->attrs[BATADV_ATTR_GW_BANDWIDTH_DOWN]) {
---
base-commit: 421d467dc2d483175bad4fb76a31b9e5a3d744cf
change-id: 20230821-batadv-missing-mtu-rtnl-lock-bc4cee67731d
Best regards,
--
Sven Eckelmann <sven@narfation•org>
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH net] batman-adv: Hold rtnl lock during MTU update via netlink
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
2023-08-23 0:30 ` patchwork-bot+netdevbpf
1 sibling, 0 replies; 3+ messages in thread
From: Simon Horman @ 2023-08-22 7:55 UTC (permalink / raw)
To: Sven Eckelmann
Cc: David S. Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni,
b.a.t.m.a.n, netdev, stable, syzbot+f8812454d9b3ac00d282
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
...
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH net] batman-adv: Hold rtnl lock during MTU update via netlink
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
@ 2023-08-23 0:30 ` patchwork-bot+netdevbpf
1 sibling, 0 replies; 3+ messages in thread
From: patchwork-bot+netdevbpf @ 2023-08-23 0:30 UTC (permalink / raw)
To: Sven Eckelmann
Cc: davem, edumazet, kuba, pabeni, b.a.t.m.a.n, netdev, stable,
syzbot+f8812454d9b3ac00d282
Hello:
This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel•org>:
On Mon, 21 Aug 2023 21:48:48 +0200 you 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:
>
> [...]
Here is the summary with links:
- [net] batman-adv: Hold rtnl lock during MTU update via netlink
https://git.kernel.org/netdev/net/c/987aae75fc10
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
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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
2023-08-23 0:30 ` patchwork-bot+netdevbpf
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