Re: general protection fault in af_alg_free_areq_sgls

[Eric Biggers]

On Fri, Dec 01, 2017 at 10:01:01AM -0800, syzbot wrote:
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Modules linked in:
> CPU: 1 PID: 3084 Comm: syzkaller426369 Not tainted 4.15.0-rc1+ #203
> Hardware name: Google Google Compute Engine/Google Compute Engine,
> BIOS Google 01/01/2011
> task: 000000009887e938 task.stack: 00000000ae5f34d5
> RIP: 0010:compound_head include/linux/page-flags.h:147 [inline]
> RIP: 0010:put_page include/linux/mm.h:850 [inline]
> RIP: 0010:af_alg_free_areq_sgls+0x5d1/0xab0 crypto/af_alg.c:678
> RSP: 0018:ffff8801cc2d7790 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffffff8239cc1a
> RDX: 0000000000000000 RSI: ffffffff85f44540 RDI: 0000000000000000
> RBP: ffff8801cc2d7988 R08: 1ffff1003985ae76 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 00000000fffffff4 R15: ffffed003985af24
> FS:  00000000021ae940(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020233fd0 CR3: 00000001cb97b000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  af_alg_free_resources+0x36/0x80 crypto/af_alg.c:1030
>  _aead_recvmsg crypto/algif_aead.c:316 [inline]
>  aead_recvmsg+0x14e1/0x1bc0 crypto/algif_aead.c:329
>  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

#syz fix: crypto: af_alg - fix NULL pointer dereference in