Re: [PATCH] net: erspan: set lltx to avoid sch_direct_xmit deadlock

[Zhou, Yun]

On 7/9/26 16:16, Paolo Abeni wrote:
> CAUTION: This email comes from a non Wind River email account!
> Do not click links or open attachments unless you recognize the sender and know the content is safe.
>
> On 7/9/26 8:56 AM, Yun Zhou wrote:
> > erspan_xmit() re-enters the network stack via ip_tunnel_xmit(), causing
> > nested acquisition of _xmit_lock on the underlay device while already
> > holding the ERSPAN device's _xmit_lock. Both are ARPHRD_ETHER and share
> > the same lockdep class, creating an ABBA deadlock:
> >
> >    sch_direct_xmit [lock erspan] -> erspan_xmit -> ip_tunnel_xmit ->
> >    ip_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 erspan_xmit() has no shared mutable state: o_seqno is
> > atomic, stats use atomic_long_inc, and dst_cache is per-CPU. GRETAP,
> > the sibling device with identical xmit structure, already sets lltx.
> >
> > Closes: https://syzkaller.appspot.com/bug?extid=9bda1b9fbb7fbdf9b62b
> > Reported-by: syzbot+9bda1b9fbb7fbdf9b62b@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Fixes: 84e54fe0a5ea ("gre: introduce native tunnel support for ERSPAN")
> > Signed-off-by: Yun Zhou <yun.zhou@xxxxxxxxxxxxx>
> So this is actually a v2 of:
>
> 20260630183702.170798-2-hemendranaik@xxxxxxxxx/20260630183702.170798-2-hemendranaik@xxxxxxxxx/
>
> right?
>
> please have a look at:
>
> https://elixir.bootlin.com/linux/v7.1/source/Documentation/process/maintainer-netdev.rst#L434
>
> any kind of re-submission matters, no matter how trivial is the reason.
>
> /P

I sincerely apologize for the duplicate patch submission. It was a minor 
oversight caused by a misconfigured Git in my new environment. However, 
it seems this email was sent to hemendranaik@xxxxxxxxx, right?

BR,
Yun