netdev - Re: [PATCH net] net/smc: prevent UAF in inet

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Message-ID: <CANn89iJXx_CG04cTaQE6ROAhvqpUOGHDQXbLc_pEY7PDiXVgxg@mail.gmail.com>
Date: Wed, 24 Jul 2024 11:32:08 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: "D. Wythe" <alibuda@...ux.alibaba.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, 
	syzbot <syzkaller@...glegroups.com>, Wenjia Zhang <wenjia@...ux.ibm.com>, 
	Dust Li <dust.li@...ux.alibaba.com>, Niklas Schnelle <schnelle@...ux.ibm.com>
Subject: Re: [PATCH net] net/smc: prevent UAF in inet_create()

On Wed, Jul 24, 2024 at 4:30 AM D. Wythe <alibuda@...ux.alibaba.com> wrote:
>
>
>
> On 7/24/24 1:58 AM, Eric Dumazet wrote:
> > Following syzbot repro crashes the kernel:
> >
> > socketpair(0x2, 0x1, 0x100, &(0x7f0000000140)) (fail_nth: 13)
> >
> > Fix this by not calling sk_common_release() from smc_create_clcsk().
> >
> > Stack trace:
> > socket: no more sockets
> > ------------[ cut here ]------------
> > refcount_t: underflow; use-after-free.
> >   WARNING: CPU: 1 PID: 5092 at lib/refcount.c:28 refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28
> > Modules linked in:
> > CPU: 1 PID: 5092 Comm: syz-executor424 Not tainted 6.10.0-syzkaller-04483-g0be9ae5486cd #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
> >   RIP: 0010:refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28
> > Code: 80 f3 1f 8c e8 e7 69 a8 fc 90 0f 0b 90 90 eb 99 e8 cb 4f e6 fc c6 05 8a 8d e8 0a 01 90 48 c7 c7 e0 f3 1f 8c e8 c7 69 a8 fc 90 <0f> 0b 90 90 e9 76 ff ff ff e8 a8 4f e6 fc c6 05 64 8d e8 0a 01 90
> > RSP: 0018:ffffc900034cfcf0 EFLAGS: 00010246
> > RAX: 3b9fcde1c862f700 RBX: ffff888022918b80 RCX: ffff88807b39bc00
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> > RBP: 0000000000000003 R08: ffffffff815878a2 R09: fffffbfff1c39d94
> > R10: dffffc0000000000 R11: fffffbfff1c39d94 R12: 00000000ffffffe9
> > R13: 1ffff11004523165 R14: ffff888022918b28 R15: ffff888022918b00
> > FS:  00005555870e7380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000020000140 CR3: 000000007582e000 CR4: 00000000003506f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >   <TASK>
> >   inet_create+0xbaf/0xe70
> >    __sock_create+0x490/0x920 net/socket.c:1571
> >    sock_create net/socket.c:1622 [inline]
> >    __sys_socketpair+0x2ca/0x720 net/socket.c:1769
> >    __do_sys_socketpair net/socket.c:1822 [inline]
> >    __se_sys_socketpair net/socket.c:1819 [inline]
> >    __x64_sys_socketpair+0x9b/0xb0 net/socket.c:1819
> >    do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> >    do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
> >   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > RIP: 0033:0x7fbcb9259669
> > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 a1 1a 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> > RSP: 002b:00007fffe931c6d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000035
> > RAX: ffffffffffffffda RBX: 00007fffe931c6f0 RCX: 00007fbcb9259669
> > RDX: 0000000000000100 RSI: 0000000000000001 RDI: 0000000000000002
> > RBP: 0000000000000002 R08: 00007fffe931c476 R09: 00000000000000a0
> > R10: 0000000020000140 R11: 0000000000000246 R12: 00007fffe931c6ec
> > R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
> >   </TASK>
>
> Oops, that's my bad, I forgot the differences in failure handling
> between smc_create and inet_create,
> thanks for your fix.
>
> >
> > Fixes: d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC")
> > Reported-by: syzbot <syzkaller@...glegroups.com>
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > Cc: D. Wythe <alibuda@...ux.alibaba.com>
> > Cc: Wenjia Zhang <wenjia@...ux.ibm.com>
> > Cc: Dust Li <dust.li@...ux.alibaba.com>
> > Cc: Niklas Schnelle <schnelle@...ux.ibm.com>
> > ---
> >   net/smc/af_smc.c | 4 +---
> >   1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
> > index 73a875573e7ad5b7a95f7941e33f0d784a91d16d..31b5d8c8c34085b73b011c913cfe032f025cd2e0 100644
> > --- a/net/smc/af_smc.c
> > +++ b/net/smc/af_smc.c
> > @@ -3319,10 +3319,8 @@ int smc_create_clcsk(struct net *net, struct sock *sk, int family)
> >
> >       rc = sock_create_kern(net, family, SOCK_STREAM, IPPROTO_TCP,
> >                             &smc->clcsock);
> > -     if (rc) {
> > -             sk_common_release(sk);
> > +     if (rc)
> >               return rc;
> > -     }
>
> Since __smc_create (for AF_SMC) does not call sk_common_release on failure,
> I think it should be moved to __smc_create instead of beingdeleted.

Please provide an updated and tested patch, thanks.