Re: WARNING: suspicious RCU usage (3)

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 28 Nov 2017 12:45:01 -0800 syzbot <bot+73a7bec1bc0f4fc0512a246334081f8c671762a8@syzkaller.appspotmail.com> wrote:

> Hello,
> 
> syzkaller hit the following crash on  
> b0a84f19a5161418d4360cd57603e94ed489915e
> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> 
> Unfortunately, I don't have any reproducer for this bug yet.
> 
> 
> WARNING: suspicious RCU usage

There's a bunch of other info which lockdep_rcu_suspicious() should
have printed out, but this trace doesn't have any of it.  I wonder why.

> 4.14.0-next-20171127+ #53 Not tainted
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000074
> IP: virt_to_cache mm/slab.c:400 [inline]
> IP: kfree+0xb2/0x250 mm/slab.c:3803
> PGD 1cd9be067 P4D 1cd9be067 PUD 1c646d067 PMD 0
> Oops: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
>     (ftrace buffer empty)
> Modules linked in:
> CPU: 1 PID: 17319 Comm: syz-executor7 Not tainted 4.14.0-next-20171127+ #53
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> task: ffff8801c5442040 task.stack: ffff8801c7ed8000
> RIP: 0010:virt_to_cache mm/slab.c:400 [inline]
> RIP: 0010:kfree+0xb2/0x250 mm/slab.c:3803
> RSP: 0018:ffff8801c7edf780 EFLAGS: 00010046
> RAX: 0000000000000000 RBX: ffff8801c7edf948 RCX: ffffffffffffffff
> RDX: ffffea00071fb7c0 RSI: 0000000000000000 RDI: ffff8801c7edf948
> RBP: ffff8801c7edf7a0 R08: ffffed003b02866c R09: 0000000000000000
> R10: 0000000000000001 R11: ffffed003b02866b R12: 0000000000000286
> R13: 0000000000000000 R14: ffff8801c7edf948 R15: ffff8801c7edf8b0
> FS:  00007ff14d179700(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000074 CR3: 00000001c6768000 CR4: 00000000001426e0
> Call Trace:
>   blkcipher_walk_done+0x72b/0xde0 crypto/blkcipher.c:139
>   encrypt+0x50a/0xaf0 crypto/salsa20_generic.c:208
>   skcipher_crypt_blkcipher crypto/skcipher.c:622 [inline]
>   skcipher_encrypt_blkcipher+0x213/0x310 crypto/skcipher.c:631
>   crypto_skcipher_encrypt include/crypto/skcipher.h:445 [inline]
>   _skcipher_recvmsg crypto/algif_skcipher.c:144 [inline]
>   skcipher_recvmsg+0x9e8/0xf20 crypto/algif_skcipher.c:165
>   sock_recvmsg_nosec net/socket.c:805 [inline]
>   sock_recvmsg+0xc9/0x110 net/socket.c:812
>   ___sys_recvmsg+0x29b/0x630 net/socket.c:2207
>   __sys_recvmsg+0xe2/0x210 net/socket.c:2252
>   SYSC_recvmsg net/socket.c:2264 [inline]
>   SyS_recvmsg+0x2d/0x50 net/socket.c:2259
>   entry_SYSCALL_64_fastpath+0x1f/0x96

It looks like blkcipher_walk_done() passed a bad address to kfree().

> RIP: 0033:0x4529d9
> RSP: 002b:00007ff14d178c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002f
> RAX: ffffffffffffffda RBX: 0000000000758190 RCX: 00000000004529d9
> RDX: 0000000000010000 RSI: 0000000020d63fc8 RDI: 0000000000000018
> RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f2728
> R13: 00000000ffffffff R14: 00007ff14d1796d4 R15: 0000000000000000
> Code: c2 48 b8 00 00 00 00 00 ea ff ff 48 89 df 48 c1 ea 0c 48 c1 e2 06 48  
> 01 c2 48 8b 42 20 48 8d 48 ff a8 01 48 0f 45 d1 4c 8b 6a 30 <49> 63 75 74  
> e8 b5 5c af ff 48 89 de 4c 89 ef 4c 8b 75 08 e8 76
> RIP: virt_to_cache mm/slab.c:400 [inline] RSP: ffff8801c7edf780
> RIP: kfree+0xb2/0x250 mm/slab.c:3803 RSP: ffff8801c7edf780
> CR2: 0000000000000074
> ---[ end trace e3c719a9c9d01886 ]---
> 
> 
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@googlegroups.com.
> Please credit me with: Reported-by: syzbot <syzkaller@googlegroups.com>
> 
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