Re: general protection fault in af_alg_free_areq_sgls

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