=============================
BUG: unable to handle kernel NULL pointer dereference at 000000009202ffd4
IP: virt_to_cache mm/slab.c:400 [inline]
IP: kfree+0xb2/0x250 mm/slab.c:3802
PGD 1c2b72067 P4D 1c2b72067 PUD 1c1963067 PMD 0 
Oops: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 21022 Comm: syz-executor6 Not tainted 4.15.0-rc1+ #136
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: 000000006f9a5f81 task.stack: 00000000c7cbec73
RIP: 0010:virt_to_cache mm/slab.c:400 [inline]
RIP: 0010:kfree+0xb2/0x250 mm/slab.c:3802
RSP: 0018:ffff8801a4997780 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff8801a4997948 RCX: ffffffffffffffff
RDX: ffffea00069265c0 RSI: 0000000000000000 RDI: ffff8801a4997948
RBP: ffff8801a49977a0 R08: ffff8801cffdf740 R09: ffff8801c38f6f00
R10: ffff8801a4997950 R11: 0000000000000108 R12: 0000000000000286
R13: 0000000000000000 R14: ffff8801a4997948 R15: ffff8801a49978b0
FS:  00007f127f619700(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000074 CR3: 000000019f1ff000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 blkcipher_walk_done+0x72b/0xde0 crypto/blkcipher.c:139
 encrypt+0x20e/0x540 arch/x86/crypto/salsa20_glue.c:79
 skcipher_crypt_blkcipher crypto/skcipher.c:622 [inline]
 skcipher_decrypt_blkcipher+0x213/0x310 crypto/skcipher.c:640
 crypto_skcipher_decrypt include/crypto/skcipher.h:463 [inline]
 _skcipher_recvmsg crypto/algif_skcipher.c:144 [inline]
 skcipher_recvmsg+0xa54/0xf20 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
RIP: 0033:0x4529d9
RSP: 002b:00007f127f618c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 00000000004529d9
RDX: 0000000000002020 RSI: 0000000020b2dfc8 RDI: 0000000000000014
RBP: 0000000000000473 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f3b68
R13: 00000000ffffffff R14: 00007f127f6196d4 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 95 75 af ff 48 89 de 4c 89 ef 4c 8b 75 08 e8 06 
RIP: virt_to_cache mm/slab.c:400 [inline] RSP: ffff8801a4997780
RIP: kfree+0xb2/0x250 mm/slab.c:3802 RSP: ffff8801a4997780
CR2: 0000000000000074
---[ end trace 63648863587468aa ]---