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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 > Signed-off-by: Yun Zhou Reviewed-by: Ido Schimmel