netdev - Re: [PATCH net] rxrpc: bad unlock balance in rxrpc

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Message-ID: <6565.1549487138@warthog.procyon.org.uk>
Date:   Wed, 06 Feb 2019 21:05:38 +0000
From:   David Howells <dhowells@...hat.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     dhowells@...hat.com, "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net] rxrpc: bad unlock balance in rxrpc_recvmsg

Eric Dumazet <edumazet@...gle.com> wrote:

> When either "goto wait_interrupted;" or "goto wait_error;"
> paths are taken, socket lock has already been released.
> 
> This patch fixes following syzbot splat :
> 
> WARNING: bad unlock balance detected!
> 5.0.0-rc4+ #59 Not tainted
> -------------------------------------
> syz-executor223/8256 is trying to release lock (sk_lock-AF_RXRPC) at:
> [<ffffffff86651353>] rxrpc_recvmsg+0x6d3/0x3099 net/rxrpc/recvmsg.c:598
> but there are no more locks to release!
> 
> other info that might help us debug this:
> 1 lock held by syz-executor223/8256:
>  #0: 00000000fa9ed0f4 (slock-AF_RXRPC){+...}, at: spin_lock_bh include/linux/spinlock.h:334 [inline]
>  #0: 00000000fa9ed0f4 (slock-AF_RXRPC){+...}, at: release_sock+0x20/0x1c0 net/core/sock.c:2798
> 
> stack backtrace:
> CPU: 1 PID: 8256 Comm: syz-executor223 Not tainted 5.0.0-rc4+ #59
> 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+0x172/0x1f0 lib/dump_stack.c:113
>  print_unlock_imbalance_bug kernel/locking/lockdep.c:3391 [inline]
>  print_unlock_imbalance_bug.cold+0x114/0x123 kernel/locking/lockdep.c:3368
>  __lock_release kernel/locking/lockdep.c:3601 [inline]
>  lock_release+0x67e/0xa00 kernel/locking/lockdep.c:3860
>  sock_release_ownership include/net/sock.h:1471 [inline]
>  release_sock+0x183/0x1c0 net/core/sock.c:2808
>  rxrpc_recvmsg+0x6d3/0x3099 net/rxrpc/recvmsg.c:598
>  sock_recvmsg_nosec net/socket.c:794 [inline]
>  sock_recvmsg net/socket.c:801 [inline]
>  sock_recvmsg+0xd0/0x110 net/socket.c:797
>  __sys_recvfrom+0x1ff/0x350 net/socket.c:1845
>  __do_sys_recvfrom net/socket.c:1863 [inline]
>  __se_sys_recvfrom net/socket.c:1859 [inline]
>  __x64_sys_recvfrom+0xe1/0x1a0 net/socket.c:1859
>  do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x446379
> Code: e8 2c b3 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 2b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fe5da89fd98 EFLAGS: 00000246 ORIG_RAX: 000000000000002d
> RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 0000000000446379
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
> RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c
> R13: 0000000000000000 R14: 0000000000000000 R15: 20c49ba5e353f7cf
> 
> Fixes: 248f219cb8bc ("rxrpc: Rewrite the data and ack handling code")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: David Howells <dhowells@...hat.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Acked-by: David Howells <dhowells@...hat.com>