lkml.org 
[lkml]   [2017]   [Nov]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: general protection fault in crypto_chacha20_crypt
On Tue, Nov 28, 2017 at 06:22:01AM -0800, syzbot wrote:
> 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

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"

\
 
 \ /
  Last update: 2017-11-29 10:25    [W:0.057 / U:0.392 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site