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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)
Fixes: c738e4751e82 ("batman-adv: Merge bugfixes from 2023.2")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
36 lines
1.4 KiB
Diff
36 lines
1.4 KiB
Diff
From: Sven Eckelmann <sven@narfation.org>
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Date: Mon, 21 Aug 2023 21:48:48 +0200
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Subject: batman-adv: Hold rtnl lock during MTU update via netlink
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The automatic recalculation of the maximum allowed MTU is usually triggered
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by code sections which are already rtnl lock protected by callers outside
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of batman-adv. But when the fragmentation setting is changed via
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batman-adv's own batadv genl family, then the rtnl lock is not yet taken.
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But dev_set_mtu requires that the caller holds the rtnl lock because it
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uses netdevice notifiers. And this code will then fail the check for this
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lock:
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RTNL: assertion failed at net/core/dev.c (1953)
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Cc: stable@vger.kernel.org
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Reported-by: syzbot+f8812454d9b3ac00d282@syzkaller.appspotmail.com
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Fixes: 27c4d7c1c7fa ("batman-adv: Trigger events for auto adjusted MTU")
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Reviewed-by: Simon Horman <horms@kernel.org>
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Signed-off-by: Sven Eckelmann <sven@narfation.org>
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Origin: upstream, https://git.open-mesh.org/batman-adv.git/commit/aeb35331aa9a17f9affd84c1a5b020aeb4a976f4
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--- a/net/batman-adv/netlink.c
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+++ b/net/batman-adv/netlink.c
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@@ -495,7 +495,10 @@ static int batadv_netlink_set_mesh(struc
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attr = info->attrs[BATADV_ATTR_FRAGMENTATION_ENABLED];
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atomic_set(&bat_priv->fragmentation, !!nla_get_u8(attr));
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+
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+ rtnl_lock();
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batadv_update_min_mtu(bat_priv->soft_iface);
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+ rtnl_unlock();
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}
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if (info->attrs[BATADV_ATTR_GW_BANDWIDTH_DOWN]) {
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