Re: [PATCH net] strparser: make sure __strp_recv isn't running before tearing down the parser

[Sabrina Dubroca <sd@queasysnail.net>]

2026-09-28, 17:23:57 +0800, Jiayuan Chen wrote:
> 
> On 9/25/26 9:51 PM, Sabrina Dubroca wrote:
> > The comment above strp_done() claims that if strp is stopped,
> > strp_recv will no longer be called. That's only true if the caller has
> > a mechanism (eg locking) to guarantee that strp_recv() calls that
> > started before strp_stop() have completed by the time we call
> > strp_done().
> > 
> > This adds a lock_sock/release_sock pair to guarantee that any
> > in-flight strp_recv() (which runs under either bh_lock_sock or
> > lock_sock, depending if it's called from ->sk_data_ready or strp_work)
> > has completed.
> > 
> > Only espintcp can be affected by this race condition, but this patch
> > makes sure no future user of strp can have the bug.
> > 
> > Reported-by: Hyunwoo Kim <imv4bel@gmail.com>
> > Link: https://lore.kernel.org/all/aZgpkyTDU3aXe_V0@v4bel/
> > Fixes: e27cca96cd68 ("xfrm: add espintcp (RFC 8229)")
> > Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
> > ---
> > This could crash on strp->sk ("general mode" of strp), but this mode
> > has been here for 9 years and has never been used. I'll send a
> > net-next patch to get rid of it.
> > 
> >   net/strparser/strparser.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> > 
> > diff --git a/net/strparser/strparser.c b/net/strparser/strparser.c
> > index a23f4b4dfc67..401e67533005 100644
> > --- a/net/strparser/strparser.c
> > +++ b/net/strparser/strparser.c
> > @@ -511,6 +511,10 @@ void strp_done(struct strparser *strp)
> >   {
> >   	WARN_ON(!strp->stopped);
> > +	lock_sock(strp->sk);
> > +	/* sync with pending strp_recv */
> > +	release_sock(strp->sk);
> > +
> 
> 
> Using sk directly inside strparser breaks the abstraction and that's why cb
> exists.
> 
> We can totally use it instead
>     strp->cb.lock(strp);
>     strp->cb.unlock(strp);

That's what I'm saying above the diffstat. This cb abstraction hasn't
been used in the 9 years it's existed, we should get rid of those
useless indirections (I'll have the patch out on netdev this week).

-- 
Sabrina