general protection fault in crypto_chacha20_crypt

[syzbot]

Hello,

syzkaller hit the following crash on
0c86a6bd85ff0629cd2c5141027fc1c8bb6cde9c
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


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: 0 PID: 6285 Comm: syzkaller774851 Not tainted 4.14.0+ #128
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
task: ffff8801c63fa140 task.stack: ffff8801c52e8000
RIP: 0010:__le32_to_cpup include/uapi/linux/byteorder/little_endian.h:58
[inline]
RIP: 0010:le32_to_cpuvp crypto/chacha20_generic.c:19 [inline]
RIP: 0010:crypto_chacha20_init crypto/chacha20_generic.c:58 [inline]
RIP: 0010:crypto_chacha20_crypt+0x537/0xbd0 crypto/chacha20_generic.c:91
RSP: 0018:ffff8801c52ef5b0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 00000000ef9ecba1 RCX: ffffffff82265bab
RDX: 0000000000000000 RSI: ffff8801c5554780 RDI: ffff8801c52ef64c
RBP: ffff8801c52ef7d0 R08: ffffed0038a8ee6c R09: ffff8801c5477340
R10: ffff8801c52ef7f0 R11: ffffed0038a8ee6b R12: 0000000000000000
R13: 0000000000000000 R14: 000000005c3d10a6 R15: dffffc0000000000
FS: 00007f7725fce700(0000) GS:ffff8801db400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020216000 CR3: 00000001c5566000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
chacha20_simd+0xe4/0x410 arch/x86/crypto/chacha20_glue.c:78
crypto_skcipher_decrypt include/crypto/skcipher.h:463 [inline]
_skcipher_recvmsg crypto/algif_skcipher.c:133 [inline]
skcipher_recvmsg+0xb06/0xf30 crypto/algif_skcipher.c:164
skcipher_recvmsg_nokey+0x60/0x80 crypto/algif_skcipher.c:283
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: 0033:0x447ae9
RSP: 002b:00007f7725fcdd08 EFLAGS: 00000246 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000447ae9
RDX: 0000000040010101 RSI: 000000002008dfc8 RDI: 0000000000000006
RBP: 0000000000000086 R08: 00007f7725fce700 R09: 00007f7725fce700
R10: 00007f7725fce700 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000007efd4f R14: 00007f7725fce9c0 R15: 0000000000000000
Code: 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 d6 05 00 00 4c 89 ea
48 b8 00 00 00 00 00 fc ff df 89 9d 7c fe ff ff 48 c1 ea 03 <0f> b6 14 02
4c 89 e8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85
RIP: __le32_to_cpup include/uapi/linux/byteorder/little_endian.h:58
[inline] RSP: ffff8801c52ef5b0
RIP: le32_to_cpuvp crypto/chacha20_generic.c:19 [inline] RSP:
ffff8801c52ef5b0
RIP: crypto_chacha20_init crypto/chacha20_generic.c:58 [inline] RSP:
ffff8801c52ef5b0
RIP: crypto_chacha20_crypt+0x537/0xbd0 crypto/chacha20_generic.c:91 RSP:
ffff8801c52ef5b0
general protection fault: 0000 [#2] SMP KASAN
---[ end trace 1cc7676745ebac7c ]---


---
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[Eric Biggers]

The bug is that the skcipher_walk API doesn't set the IV for zero-length inputs,
while some algorithms (e.g. ChaCha20) access the IV even if the input is
zero-length. So it was dereferencing a pointer which came from uninitialized
stack memory. I've sent out a fix:

"crypto: skcipher - set walk.iv for zero-length inputs"

[Eric Biggers]

On Wed, Nov 29, 2017 at 01:24:38AM -0800, Eric Biggers wrote:
>
> The bug is that the skcipher_walk API doesn't set the IV for zero-length inputs,
> while some algorithms (e.g. ChaCha20) access the IV even if the input is
> zero-length. So it was dereferencing a pointer which came from uninitialized
> stack memory. I've sent out a fix:
>
> "crypto: skcipher - set walk.iv for zero-length inputs"
>

#syz fix: crypto: skcipher - set walk.iv for zero-length inputs