netdev - Re: [PATCH net] rds: fix refcount bug in rds_sock

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Date:   Thu, 31 Jan 2019 09:16:21 -0800
From:   Santosh Shilimkar <santosh.shilimkar@...cle.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        syzbot <syzkaller@...glegroups.com>,
        Sowmini Varadhan <sowmini.varadhan@...cle.com>,
        rds-devel@....oracle.com, Cong Wang <xiyou.wangcong@...il.com>
Subject: Re: [PATCH net] rds: fix refcount bug in rds_sock_addref

On 1/31/2019 8:47 AM, Eric Dumazet wrote:
> syzbot was able to catch a bug in rds [1]
> 
> The issue here is that the socket might be found in a hash table
> but that its refcount has already be set to 0 by another cpu.
> 
> We need to use refcount_inc_not_zero() to be safe here.
> 
> [1]
> 
> refcount_t: increment on 0; use-after-free.
> WARNING: CPU: 1 PID: 23129 at lib/refcount.c:153 refcount_inc_checked lib/refcount.c:153 [inline]
> WARNING: CPU: 1 PID: 23129 at lib/refcount.c:153 refcount_inc_checked+0x61/0x70 lib/refcount.c:151
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 1 PID: 23129 Comm: syz-executor3 Not tainted 5.0.0-rc4+ #53
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
>   panic+0x2cb/0x65c kernel/panic.c:214
>   __warn.cold+0x20/0x48 kernel/panic.c:571
>   report_bug+0x263/0x2b0 lib/bug.c:186
>   fixup_bug arch/x86/kernel/traps.c:178 [inline]
>   fixup_bug arch/x86/kernel/traps.c:173 [inline]
>   do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
>   do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:290
>   invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
> RIP: 0010:refcount_inc_checked lib/refcount.c:153 [inline]
> RIP: 0010:refcount_inc_checked+0x61/0x70 lib/refcount.c:151
> Code: 1d 51 63 c8 06 31 ff 89 de e8 eb 1b f2 fd 84 db 75 dd e8 a2 1a f2 fd 48 c7 c7 60 9f 81 88 c6 05 31 63 c8 06 01 e8 af 65 bb fd <0f> 0b eb c1 90 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 54 49
> RSP: 0018:ffff8880a0cbf1e8 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc90006113000
> RDX: 000000000001047d RSI: ffffffff81685776 RDI: 0000000000000005
> RBP: ffff8880a0cbf1f8 R08: ffff888097c9e100 R09: ffffed1015ce5021
> R10: ffffed1015ce5020 R11: ffff8880ae728107 R12: ffff8880723c20c0
> R13: ffff8880723c24b0 R14: dffffc0000000000 R15: ffffed1014197e64
>   sock_hold include/net/sock.h:647 [inline]
>   rds_sock_addref+0x19/0x20 net/rds/af_rds.c:675
>   rds_find_bound+0x97c/0x1080 net/rds/bind.c:82
>   rds_recv_incoming+0x3be/0x1430 net/rds/recv.c:362
>   rds_loop_xmit+0xf3/0x2a0 net/rds/loop.c:96
>   rds_send_xmit+0x1355/0x2a10 net/rds/send.c:355
>   rds_sendmsg+0x323c/0x44e0 net/rds/send.c:1368
>   sock_sendmsg_nosec net/socket.c:621 [inline]
>   sock_sendmsg+0xdd/0x130 net/socket.c:631
>   __sys_sendto+0x387/0x5f0 net/socket.c:1788
>   __do_sys_sendto net/socket.c:1800 [inline]
>   __se_sys_sendto net/socket.c:1796 [inline]
>   __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1796
>   do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x458089
> Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fc266df8c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
> RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 0000000000458089
> RDX: 0000000000000000 RSI: 00000000204b3fff RDI: 0000000000000005
> RBP: 000000000073bf00 R08: 00000000202b4000 R09: 0000000000000010
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007fc266df96d4
> R13: 00000000004c56e4 R14: 00000000004d94a8 R15: 00000000ffffffff
> 
> Fixes: cc4dfb7f70a3 ("rds: fix two RCU related problems")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Cc: Sowmini Varadhan <sowmini.varadhan@...cle.com>
> Cc: Santosh Shilimkar <santosh.shilimkar@...cle.com>
> Cc: rds-devel@....oracle.com
> Cc: Cong Wang <xiyou.wangcong@...il.com>
> ---
Looks good.
Acked-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>