netdev - Re: [PATCH net] net/smc: do not leave a dangling sk pointer in __smc

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Message-ID: <CANn89iJ382wPnWz11FdymoGvKgmXoKKF29_-ip3316U9puuTjg@mail.gmail.com>
Date: Thu, 7 Nov 2024 09:32:50 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Wenjia Zhang <wenjia@...ux.ibm.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Kuniyuki Iwashima <kuniyu@...zon.com>, Ignat Korchagin <ignat@...udflare.com>, 
	"D. Wythe" <alibuda@...ux.alibaba.com>, Dust Li <dust.li@...ux.alibaba.com>
Subject: Re: [PATCH net] net/smc: do not leave a dangling sk pointer in __smc_create()

On Thu, Nov 7, 2024 at 9:28 AM Wenjia Zhang <wenjia@...ux.ibm.com> wrote:
>
>
>
> On 06.11.24 23:19, Eric Dumazet wrote:
> > Thanks to commit 4bbd360a5084 ("socket: Print pf->create() when
> > it does not clear sock->sk on failure."), syzbot found an issue with AF_SMC:
> >
> > smc_create must clear sock->sk on failure, family: 43, type: 1, protocol: 0
> >   WARNING: CPU: 0 PID: 5827 at net/socket.c:1565 __sock_create+0x96f/0xa30 net/socket.c:1563
> > Modules linked in:
> > CPU: 0 UID: 0 PID: 5827 Comm: syz-executor259 Not tainted 6.12.0-rc6-next-20241106-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> >   RIP: 0010:__sock_create+0x96f/0xa30 net/socket.c:1563
> > Code: 03 00 74 08 4c 89 e7 e8 4f 3b 85 f8 49 8b 34 24 48 c7 c7 40 89 0c 8d 8b 54 24 04 8b 4c 24 0c 44 8b 44 24 08 e8 32 78 db f7 90 <0f> 0b 90 90 e9 d3 fd ff ff 89 e9 80 e1 07 fe c1 38 c1 0f 8c ee f7
> > RSP: 0018:ffffc90003e4fda0 EFLAGS: 00010246
> > RAX: 099c6f938c7f4700 RBX: 1ffffffff1a595fd RCX: ffff888034823c00
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> > RBP: 00000000ffffffe9 R08: ffffffff81567052 R09: 1ffff920007c9f50
> > R10: dffffc0000000000 R11: fffff520007c9f51 R12: ffffffff8d2cafe8
> > R13: 1ffffffff1a595fe R14: ffffffff9a789c40 R15: ffff8880764298c0
> > FS:  000055557b518380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007fa62ff43225 CR3: 0000000031628000 CR4: 00000000003526f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >   <TASK>
> >    sock_create net/socket.c:1616 [inline]
> >    __sys_socket_create net/socket.c:1653 [inline]
> >    __sys_socket+0x150/0x3c0 net/socket.c:1700
> >    __do_sys_socket net/socket.c:1714 [inline]
> >    __se_sys_socket net/socket.c:1712 [inline]
> >
> > For reference, see commit 2d859aff775d ("Merge branch
> > 'do-not-leave-dangling-sk-pointers-in-pf-create-functions'")
> >
> > Fixes: d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC")
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > Cc: Kuniyuki Iwashima <kuniyu@...zon.com>
> > Cc: Ignat Korchagin <ignat@...udflare.com>
> > Cc: D. Wythe <alibuda@...ux.alibaba.com>
> > Cc: Wenjia Zhang <wenjia@...ux.ibm.com>
> > Cc: Dust Li <dust.li@...ux.alibaba.com>
> > ---
>
> Thank you, Eric, for fixing it! The code looks good to me.
> Should the fixed commit not be 2fe5273f149c instead of d25a92ccae6b?
>

The bug was there, even before 2fe5273f149c ("net/smc: prevent UAF in
inet_create()")

Thanks.