netdev - Re: [PATCH v1 net-next] socket: Print pf->create() when it does not clear sock->sk on failure.

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Message-ID: <20241023195144.60048-1-kuniyu@amazon.com>
Date: Wed, 23 Oct 2024 12:51:44 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <edumazet@...gle.com>
CC: <davem@...emloft.net>, <ignat@...udflare.com>, <kuba@...nel.org>,
	<kuni1840@...il.com>, <kuniyu@...zon.com>, <netdev@...r.kernel.org>,
	<pabeni@...hat.com>
Subject: Re: [PATCH v1 net-next] socket: Print pf->create() when it does not clear sock->sk on failure.

From: Eric Dumazet <edumazet@...gle.com>
Date: Wed, 23 Oct 2024 21:45:26 +0200
> On Wed, Oct 23, 2024 at 9:18 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
> >
> > I suggested to put DEBUG_NET_WARN_ON_ONCE() in __sock_create() to
> > catch possible use-after-free.
> >
> > But the warning itself was not useful because our interest is in
> > the callee than the caller.
> >
> > Let's define DEBUG_NET_WARN_ONCE() and print the name of pf->create()
> > and the socket identifier.
> >
> > While at it, we enclose DEBUG_NET_WARN_ON_ONCE() in parentheses too
> > to avoid a checkpatch error.
> >
> > Note that %pf or %pF were obsoleted and later removed as per comment
> > in lib/vsprintf.c.
> >
> > Link: https://lore.kernel.org/netdev/202410231427.633734b3-lkp@intel.com/
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> > ---
> >  include/net/net_debug.h | 4 +++-
> >  net/socket.c            | 4 +++-
> >  2 files changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/net/net_debug.h b/include/net/net_debug.h
> > index 1e74684cbbdb..9fecb1496be3 100644
> > --- a/include/net/net_debug.h
> > +++ b/include/net/net_debug.h
> > @@ -149,9 +149,11 @@ do {                                                               \
> >
> >
> >  #if defined(CONFIG_DEBUG_NET)
> > -#define DEBUG_NET_WARN_ON_ONCE(cond) (void)WARN_ON_ONCE(cond)
> > +#define DEBUG_NET_WARN_ON_ONCE(cond) ((void)WARN_ON_ONCE(cond))
> > +#define DEBUG_NET_WARN_ONCE(cond, format...) ((void)WARN_ONCE(cond, format))
> >  #else
> >  #define DEBUG_NET_WARN_ON_ONCE(cond) BUILD_BUG_ON_INVALID(cond)
> > +#define DEBUG_NET_WARN_ONCE(cond, format...) BUILD_BUG_ON_INVALID(cond)
> >  #endif
> >
> >  #endif /* _LINUX_NET_DEBUG_H */
> > diff --git a/net/socket.c b/net/socket.c
> > index 9a8e4452b9b2..da00db3824e3 100644
> > --- a/net/socket.c
> > +++ b/net/socket.c
> > @@ -1578,7 +1578,9 @@ int __sock_create(struct net *net, int family, int type, int protocol,
> >                 /* ->create should release the allocated sock->sk object on error
> >                  * and make sure sock->sk is set to NULL to avoid use-after-free
> >                  */
> > -               DEBUG_NET_WARN_ON_ONCE(sock->sk);
> > +               DEBUG_NET_WARN_ONCE(sock->sk,
> > +                                   "%pS must clear sock->sk on failure, family: %d, type: %d, protocol: %d\n",
> 
> %ps would be more appropriate, the offset should be zero, no need to
> display a full 'symbol+0x0/0x<size>'

Ah, exactly!
Will use %ps in v2.

Thanks!

---
pw-bot: cr