Re: BUG: sleeping function called from invalid context at mm/slab.h:LINE (4)

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    d14b746c6c1c Add linux-next specific files for 20181214
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=129bc943400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1da6d2d18f803140
dashboard link: https://syzkaller.appspot.com/bug?extid=9bf843c33f782d73ae7d
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=136154cd400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1687bfa3400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9bf843c33f782d73ae7d@xxxxxxxxxxxxxxxxxxxxxxxxx

sshd (6035) used greatest stack depth: 15600 bytes left
BUG: sleeping function called from invalid context at mm/slab.h:421
in_atomic(): 1, irqs_disabled(): 0, pid: 6051, name: syz-executor515
1 lock held by syz-executor515/6051:
 #0: 000000002f6552ef (sk_lock-AF_ALG){+.+.}, at: lock_sock  
include/net/sock.h:1502 [inline]
 #0: 000000002f6552ef (sk_lock-AF_ALG){+.+.}, at:  
skcipher_recvmsg+0xbb/0x1420 crypto/algif_skcipher.c:163
Preemption disabled at:
[<ffffffff812e4ae6>] kernel_fpu_begin+0x16/0x260  
arch/x86/kernel/fpu/core.c:127
CPU: 0 PID: 6051 Comm: syz-executor515 Not tainted  
4.20.0-rc6-next-20181214+ #171
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x244/0x39d lib/dump_stack.c:113
 ___might_sleep.cold.86+0x221/0x254 kernel/sched/core.c:6148
 __might_sleep+0x95/0x190 kernel/sched/core.c:6101
 slab_pre_alloc_hook mm/slab.h:421 [inline]
 slab_alloc mm/slab.c:3365 [inline]
 __do_kmalloc mm/slab.c:3707 [inline]
 __kmalloc+0x2da/0x760 mm/slab.c:3718
 kmalloc include/linux/slab.h:550 [inline]
 kzalloc include/linux/slab.h:740 [inline]
 skcipher_next_slow crypto/skcipher.c:254 [inline]
 skcipher_walk_next+0x7f9/0x17f0 crypto/skcipher.c:358
 skcipher_walk_first+0xff/0x3a0 crypto/skcipher.c:441
 skcipher_walk_skcipher+0x541/0x700 crypto/skcipher.c:469
 skcipher_walk_virt+0x58/0xd0 crypto/skcipher.c:479
 chacha_simd_stream_xor+0xb3/0xa40 arch/x86/crypto/chacha_glue.c:141
 chacha_simd+0xd8/0x110 arch/x86/crypto/chacha_glue.c:179
 crypto_skcipher_decrypt include/crypto/skcipher.h:538 [inline]
 _skcipher_recvmsg crypto/algif_skcipher.c:146 [inline]
 skcipher_recvmsg+0xcc9/0x1420 crypto/algif_skcipher.c:165
 sock_recvmsg_nosec net/socket.c:795 [inline]
 sock_recvmsg+0xd0/0x110 net/socket.c:802
 ___sys_recvmsg+0x2b6/0x680 net/socket.c:2279
 do_recvmmsg+0x303/0xb90 net/socket.c:2392
 __sys_recvmmsg+0x265/0x2a0 net/socket.c:2471
 __do_sys_recvmmsg net/socket.c:2494 [inline]
 __se_sys_recvmmsg net/socket.c:2487 [inline]
 __x64_sys_recvmmsg+0xe6/0x140 net/socket.c:2487
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440349
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff9312c608 EFLAGS: 00000203 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440349
RDX: 0000000000000001 RSI: 000000002000a280 RDI: 0000000000000004
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000203 R12: 00000000