diff options
| author | Yun Zhou <yun.zhou@windriver.com> | 2026-10-08 17:38:24 +0800 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-10-15 17:18:00 -0700 |
| commit | 2d36ec73836e83175deb467fd494c61006107e5d (patch) | |
| tree | b528aaad22f94edd4b78f4e76e0477045b651afa /net/ipv6 | |
| parent | ee3deb0151d3604ff5d4474262f6d942bd3f372f (diff) | |
net: erspan: set lltx to avoid sch_direct_xmit deadlock
The ERSPAN xmit path re-enters the network stack, causing nested
acquisition of _xmit_lock on the underlay device while already holding
the ERSPAN device's _xmit_lock, creating an ABBA deadlock. This happens
for both IPv4 ERSPAN (erspan_xmit() -> ip_tunnel_xmit()) and IPv6 ERSPAN
(ip6erspan_tunnel_xmit() -> ip6_tnl_xmit()):
sch_direct_xmit [lock erspan] -> erspan_xmit -> ip_tunnel_xmit ->
ip_output -> __dev_queue_xmit -> sch_direct_xmit [lock underlay]
sch_direct_xmit [lock erspan] -> ip6erspan_tunnel_xmit -> ip6_tnl_xmit ->
ip6_output -> __dev_queue_xmit -> sch_direct_xmit [lock underlay]
Set dev->lltx = true so HARD_TX_LOCK() skips the spinlock for ERSPAN.
This is safe as the ERSPAN xmit path has no shared mutable state: o_seqno
is atomic, TX stats are per-CPU u64_stats, dst_cache is per-CPU, and
o_flags is no longer modified in the xmit path since commit 9958e69b9893
("gre: fix ERSPAN o_flags race/corruption in xmit and fill_info").
GRETAP, the sibling device with identical xmit structure, already sets
lltx.
Reported-by: syzbot+9bda1b9fbb7fbdf9b62b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=9bda1b9fbb7fbdf9b62b
Fixes: 84e54fe0a5ea ("gre: introduce native tunnel support for ERSPAN")
Fixes: 5a963eb61b7c ("ip6_gre: Add ERSPAN native tunnel support")
Cc: stable@vger.kernel.org # 9958e69b9893 ("gre: fix ERSPAN o_flags race/corruption in xmit and fill_info")
Cc: stable@vger.kernel.org
Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20261008093824.119453-1-yun.zhou@windriver.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/ipv6')
| -rw-r--r-- | net/ipv6/ip6_gre.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index 04f7c70b7320..3429543ec77e 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -1864,6 +1864,7 @@ static int ip6erspan_tap_init(struct net_device *dev) dev->mtu -= 8; dev->priv_flags |= IFF_LIVE_ADDR_CHANGE; + dev->lltx = true; ip6erspan_tnl_link_config(tunnel, 1); netdev_hold(dev, &tunnel->dev_tracker, GFP_KERNEL); |