=============================
WARNING: suspicious RCU usage
4.15.0-rc1-mm1+ #28 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 1c91b2067 P4D 1c91b2067 PUD 1d284e067 PMD 0 
Oops: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 13346 Comm: syz-executor6 Not tainted 4.15.0-rc1-mm1+ #28
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9326380 task.stack: ffff8801c79f0000
RIP: 0010:virt_to_cache mm/slab.c:400 [inline]
RIP: 0010:kfree+0xb2/0x250 mm/slab.c:3803
RSP: 0018:ffff8801c79f75e0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff8801c79f77a8 RCX: ffffffffffffffff
RDX: ffffea00071e7dc0 RSI: 0000000000000000 RDI: ffff8801c79f77a8
RBP: ffff8801c79f7600 R08: ffffed0038368504 R09: 0000000000000000
R10: 0000000000000001 R11: ffffed0038368503 R12: 0000000000000282
R13: 0000000000000000 R14: ffff8801c79f77a8 R15: ffff8801c79f7710
FS:  00007fd19e8bd700(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000074 CR3: 00000001c359d000 CR4: 00000000001406e0
DR0: 0000000020000008 DR1: 0000000020000008 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
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_recvmmsg+0x2a9/0xaf0 net/socket.c:2315
 SYSC_recvmmsg net/socket.c:2396 [inline]
 SyS_recvmmsg+0xc4/0x160 net/socket.c:2380
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x4529d9
RSP: 002b:00007fd19e8bcc58 EFLAGS: 00000212 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007fd19e8bd700 RCX: 00000000004529d9
RDX: 0000000000000002 RSI: 0000000020ee1f88 RDI: 0000000000000015
RBP: 0000000000a6f880 R08: 0000000020000000 R09: 0000000000000000
R10: 0000000000000020 R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a6f7ff R14: 00007fd19e8bd9c0 R15: 0000000000000001
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 d5 59 af ff 48 89 de 4c 89 ef 4c 8b 75 08 e8 76 
RIP: virt_to_cache mm/slab.c:400 [inline] RSP: ffff8801c79f75e0
RIP: kfree+0xb2/0x250 mm/slab.c:3803 RSP: ffff8801c79f75e0
CR2: 0000000000000074
---[ end trace 5597090f51f1eb4e ]---