Date:   Mon, 8 Jan 2018 18:01:14 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     syzbot <syzbot+ac6ea7baa4432811eb50@...kaller.appspotmail.com>
Cc:     davem <davem@...emloft.net>, LKML <linux-kernel@...r.kernel.org>,
        linux-sctp@...r.kernel.org, network dev <netdev@...r.kernel.org>,
        Neil Horman <nhorman@...driver.com>,
        syzkaller-bugs@...glegroups.com,
        Vlad Yasevich <vyasevich@...il.com>
Subject: Re: WARNING: held lock freed!

On Mon, Jan 8, 2018 at 6:58 AM, syzbot
<syzbot+ac6ea7baa4432811eb50@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzkaller hit the following crash on
> 3219e264b984ec0a13923aa66385819c2e98d582
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
>
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+ac6ea7baa4432811eb50@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
>
>
> =========================
> WARNING: held lock freed!
> 4.15.0-rc6+ #250 Not tainted
> -------------------------
> syzkaller065230/3505 is freeing memory 000000007fcba654-00000000499fef26,
> with a lock still held there!
>  (sk_lock-AF_INET6){+.+.}, at: [<00000000abe26b8e>] lock_sock
> include/net/sock.h:1461 [inline]
>  (sk_lock-AF_INET6){+.+.}, at: [<00000000abe26b8e>]
> sctp_wait_for_sndbuf+0x509/0x8d0 net/sctp/socket.c:8042
> 1 lock held by syzkaller065230/3505:
>  #0:  (sk_lock-AF_INET6){+.+.}, at: [<00000000abe26b8e>] lock_sock
> include/net/sock.h:1461 [inline]
>  #0:  (sk_lock-AF_INET6){+.+.}, at: [<00000000abe26b8e>]
> sctp_wait_for_sndbuf+0x509/0x8d0 net/sctp/socket.c:8042
>
> stack backtrace:
> CPU: 0 PID: 3505 Comm: syzkaller065230 Not tainted 4.15.0-rc6+ #250
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:53
>  print_freed_lock_bug kernel/locking/lockdep.c:4379 [inline]
>  debug_check_no_locks_freed+0x32f/0x3c0 kernel/locking/lockdep.c:4412
>  kmem_cache_free+0x68/0x2a0 mm/slab.c:3743
>  sk_prot_free net/core/sock.c:1504 [inline]
>  __sk_destruct+0x622/0x910 net/core/sock.c:1585
>  sk_destruct+0x47/0x80 net/core/sock.c:1593
>  __sk_free+0x57/0x230 net/core/sock.c:1601
>  sk_free+0x2a/0x40 net/core/sock.c:1612
>  sock_put include/net/sock.h:1656 [inline]
>  sctp_association_destroy net/sctp/associola.c:424 [inline]
>  sctp_association_put+0x14c/0x2f0 net/sctp/associola.c:883
>  sctp_wait_for_sndbuf+0x673/0x8d0 net/sctp/socket.c:8053
>  sctp_sendmsg+0x277d/0x3360 net/sctp/socket.c:1974
>  inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
>  sock_sendmsg_nosec net/socket.c:636 [inline]
>  sock_sendmsg+0xca/0x110 net/socket.c:646
>  SYSC_sendto+0x361/0x5c0 net/socket.c:1727
>  SyS_sendto+0x40/0x50 net/socket.c:1695
>  entry_SYSCALL_64_fastpath+0x23/0x9a
> RIP: 0033:0x445db9
> RSP: 002b:00007f2467415d98 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
> RAX: ffffffffffffffda RBX: 00000000006dbc84 RCX: 0000000000445db9
> RDX: 0000000000000001 RSI: 000000002010bf14 RDI: 0000000000000005
> RBP: 0000000000000000 R08: 00000000204d9000 R09: 000000000000001c
> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006dbc80
> R13: 00000000209a9000 R14: 0100000000000000 R15: 0000000000000001
> ==================================================================
> BUG: KASAN: use-after-free in debug_spin_lock_before
> kernel/locking/spinlock_debug.c:83 [inline]
> BUG: KASAN: use-after-free in do_raw_spin_lock+0x1e0/0x220
> kernel/locking/spinlock_debug.c:112
> Read of size 4 at addr ffff8801c17ab08c by task syzkaller065230/3505

It seems this commit is buggy:
commit cea0cc80a6777beb6eb643d4ad53690e1ad1d4ff
Author: Xin Long <lucien.xin@...il.com>
Date:   Wed Nov 15 16:57:26 2017 +0800

    sctp: use the right sk after waking up from wait_buf sleep

I already had a patch to drop it and fix the old issue with a better way.


>
> CPU: 0 PID: 3505 Comm: syzkaller065230 Not tainted 4.15.0-rc6+ #250
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:53
>  print_address_description+0x73/0x250 mm/kasan/report.c:252
>  kasan_report_error mm/kasan/report.c:351 [inline]
>  kasan_report+0x25b/0x340 mm/kasan/report.c:409
>  __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429
>  debug_spin_lock_before kernel/locking/spinlock_debug.c:83 [inline]
>  do_raw_spin_lock+0x1e0/0x220 kernel/locking/spinlock_debug.c:112
>  __raw_spin_lock_bh include/linux/spinlock_api_smp.h:136 [inline]
>  _raw_spin_lock_bh+0x39/0x40 kernel/locking/spinlock.c:168
>  spin_lock_bh include/linux/spinlock.h:315 [inline]
>  release_sock+0x74/0x2a0 net/core/sock.c:2777
>  sctp_sendmsg+0x2c61/0x3360 net/sctp/socket.c:2058
>  inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
>  sock_sendmsg_nosec net/socket.c:636 [inline]
>  sock_sendmsg+0xca/0x110 net/socket.c:646
>  SYSC_sendto+0x361/0x5c0 net/socket.c:1727
>  SyS_sendto+0x40/0x50 net/socket.c:1695
>  entry_SYSCALL_64_fastpath+0x23/0x9a
> RIP: 0033:0x445db9
> RSP: 002b:00007f2467415d98 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
> RAX: ffffffffffffffda RBX: 00000000006dbc84 RCX: 0000000000445db9
> RDX: 0000000000000001 RSI: 000000002010bf14 RDI: 0000000000000005
> RBP: 0000000000000000 R08: 00000000204d9000 R09: 000000000000001c
> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006dbc80
> R13: 00000000209a9000 R14: 0100000000000000 R15: 0000000000000001
>
> Allocated by task 3506:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>  set_track mm/kasan/kasan.c:459 [inline]
>  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
>  kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
>  kmem_cache_alloc+0x12e/0x760 mm/slab.c:3544
>  sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1463
>  sk_alloc+0x105/0x1410 net/core/sock.c:1523
>  sctp_v6_create_accept_sk+0x15a/0x9b0 net/sctp/ipv6.c:667
>  sctp_accept+0x5c4/0x970 net/sctp/socket.c:4314
>  inet_accept+0x12c/0x930 net/ipv4/af_inet.c:698
>  SYSC_accept4+0x38d/0x870 net/socket.c:1551
>  SyS_accept4 net/socket.c:1502 [inline]
>  SYSC_accept net/socket.c:1585 [inline]
>  SyS_accept+0x26/0x30 net/socket.c:1582
>  entry_SYSCALL_64_fastpath+0x23/0x9a
>
> Freed by task 3505:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>  set_track mm/kasan/kasan.c:459 [inline]
>  kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
>  __cache_free mm/slab.c:3488 [inline]
>  kmem_cache_free+0x83/0x2a0 mm/slab.c:3746
>  sk_prot_free net/core/sock.c:1504 [inline]
>  __sk_destruct+0x622/0x910 net/core/sock.c:1585
>  sk_destruct+0x47/0x80 net/core/sock.c:1593
>  __sk_free+0x57/0x230 net/core/sock.c:1601
>  sk_free+0x2a/0x40 net/core/sock.c:1612
>  sock_put include/net/sock.h:1656 [inline]
>  sctp_association_destroy net/sctp/associola.c:424 [inline]
>  sctp_association_put+0x14c/0x2f0 net/sctp/associola.c:883
>  sctp_wait_for_sndbuf+0x673/0x8d0 net/sctp/socket.c:8053
>  sctp_sendmsg+0x277d/0x3360 net/sctp/socket.c:1974
>  inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
>  sock_sendmsg_nosec net/socket.c:636 [inline]
>  sock_sendmsg+0xca/0x110 net/socket.c:646
>  SYSC_sendto+0x361/0x5c0 net/socket.c:1727
>  SyS_sendto+0x40/0x50 net/socket.c:1695
>  entry_SYSCALL_64_fastpath+0x23/0x9a
>
> The buggy address belongs to the object at ffff8801c17ab000
>  which belongs to the cache SCTPv6 of size 1888
> The buggy address is located 140 bytes inside of
>  1888-byte region [ffff8801c17ab000, ffff8801c17ab760)
> The buggy address belongs to the page:
> page:ffffea000705eac0 count:1 mapcount:0 mapping:ffff8801c17ab000 index:0x0
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffff8801c17ab000 0000000000000000 0000000100000002
> raw: ffffea00070173e0 ffffea0007044860 ffff8801d32b0380 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801c17aaf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff8801c17ab000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>
>> ffff8801c17ab080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>
>                       ^
>  ffff8801c17ab100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801c17ab180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@...glegroups.com.
>
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