=============================
WARNING: suspicious RCU usage
4.15.0-rc2+ #153 Not tainted
-----------------------------
./include/trace/events/kmem.h:142 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz-executor2/18010:
 #0:  (sk_lock-AF_ALG){+.+.}, at: [<00000000c7e9dd72>] lock_sock include/net/sock.h:1461 [inline]
 #0:  (sk_lock-AF_ALG){+.+.}, at: [<00000000c7e9dd72>] af_alg_wait_for_data+0x2f2/0x650 crypto/af_alg.c:768

stack backtrace:
CPU: 0 PID: 18010 Comm: syz-executor2 Not tainted 4.15.0-rc2+ #153
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4675
 trace_kfree include/trace/events/kmem.h:137 [inline]
 kfree+0x20a/0x250 mm/slab.c:3796
 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_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:809 [inline]
 sock_recvmsg+0xc9/0x110 net/socket.c:816
 SYSC_recvfrom+0x2dc/0x570 net/socket.c:1779
 SyS_recvfrom+0x40/0x50 net/socket.c:1751
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x452a39
RSP: 002b:00007fd23fa97c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002d
RAX: ffffffffffffffda RBX: 00007fd23fa98700 RCX: 0000000000452a39
RDX: 00000000000000b4 RSI: 0000000020f77f4c RDI: 0000000000000014
RBP: 0000000000000000 R08: 000000002009bff8 R09: 0000000000000008
R10: 0000000040000000 R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a6f7ff R14: 00007fd23fa989c0 R15: 0000000000000000
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:3802
PGD 1cf86e067 P4D 1cf86e067 PUD 1c82da067 PMD 0 
Oops: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 18010 Comm: syz-executor2 Not tainted 4.15.0-rc2+ #153
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:virt_to_cache mm/slab.c:400 [inline]
RIP: 0010:kfree+0xb2/0x250 mm/slab.c:3802
RSP: 0018:ffff8801cf4ff8e0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff8801cf4ffaa8 RCX: ffffffffffffffff
RDX: ffffea00073d3fc0 RSI: 0000000000000000 RDI: ffff8801cf4ffaa8
RBP: ffff8801cf4ff900 R08: 1ffff10039e9fece R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000282
R13: 0000000000000000 R14: ffff8801cf4ffaa8 R15: ffff8801cf4ffa10
FS:  00007fd23fa98700(0000) GS:ffff8801db400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000074 CR3: 00000001c3f71000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
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_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:809 [inline]
 sock_recvmsg+0xc9/0x110 net/socket.c:816
 SYSC_recvfrom+0x2dc/0x570 net/socket.c:1779
 SyS_recvfrom+0x40/0x50 net/socket.c:1751
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x452a39
RSP: 002b:00007fd23fa97c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002d
RAX: ffffffffffffffda RBX: 00007fd23fa98700 RCX: 0000000000452a39
RDX: 00000000000000b4 RSI: 0000000020f77f4c RDI: 0000000000000014
RBP: 0000000000000000 R08: 000000002009bff8 R09: 0000000000000008
R10: 0000000040000000 R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a6f7ff R14: 00007fd23fa989c0 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 05 74 af ff 48 89 de 4c 89 ef 4c 8b 75 08 e8 06 
RIP: virt_to_cache mm/slab.c:400 [inline] RSP: ffff8801cf4ff8e0
RIP: kfree+0xb2/0x250 mm/slab.c:3802 RSP: ffff8801cf4ff8e0
CR2: 0000000000000074
---[ end trace 01fc5b671e8ff8c4 ]---