Re: KASAN: use-after-free Read in crypto_morus640_decrypt_chunk

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    f0dc7f9c6dd9 Merge git://git.kernel.org/pub/scm/linux/kern..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=109f9037800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fa9c20c48788d1c1
dashboard link: https://syzkaller.appspot.com/bug?extid=d82643ba80bf6937cd44
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1799185f800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1241e1bf800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d82643ba80bf6937cd44@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: use-after-free in crypto_morus640_load_a crypto/morus640.c:111  
[inline]
BUG: KASAN: use-after-free in crypto_morus640_decrypt_chunk+0xcf8/0xd20  
crypto/morus640.c:278
Read of size 4 at addr ffff8801c0fc6003 by task syz-executor042/4573

CPU: 1 PID: 4573 Comm: syz-executor042 Not tainted 4.17.0+ #84
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+0x1b9/0x294 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 crypto_morus640_load_a crypto/morus640.c:111 [inline]
 crypto_morus640_decrypt_chunk+0xcf8/0xd20 crypto/morus640.c:278
 crypto_morus640_process_crypt.isra.12+0x153/0x230 crypto/morus640.c:376
 crypto_morus640_crypt+0x42e/0x9f0 crypto/morus640.c:442
 crypto_morus640_decrypt+0x23e/0x3d0 crypto/morus640.c:485
 crypto_aead_decrypt include/crypto/aead.h:370 [inline]
 _aead_recvmsg crypto/algif_aead.c:315 [inline]
 aead_recvmsg+0x13cc/0x1ba0 crypto/algif_aead.c:334
 sock_recvmsg_nosec net/socket.c:818 [inline]
 sock_recvmsg+0xd0/0x110 net/socket.c:825
 ___sys_recvmsg+0x2b6/0x680 net/socket.c:2323
 __sys_recvmsg+0x112/0x260 net/socket.c:2372
 __do_sys_recvmsg net/socket.c:2382 [inline]
 __se_sys_recvmsg net/socket.c:2379 [inline]
 __x64_sys_recvmsg+0x78/0xb0 net/socket.c:2379
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445b19
Code: e8 5c e7 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 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 db 51 00 00 c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f0fc4fccda8 EFLAGS: 00000297 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 00000000006dac9c RCX: 0000000000445b19
RDX: 0000000000000000 RSI: 0000000020002840 RDI: 0000000000000011
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 00000000006dac98
R13: 558bdd1ccff55d26 R14: f09319918a28f2b7 R15: 0000000000000001

The buggy address belongs to the page:
page:ffffea000703f180 count:0 mapcount:0 mapping:0000000000000000 index:0x1
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 ffffea0007208788 ffffea0007026148 0000000000000000
raw: 0000000000000038 0000000000000000 0000000200000000 ffff8801d9a42c80
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c0fc5f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801c0fc5f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8801c0fc6000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8801c0fc6080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801c0fc6100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================