KASAN: stack-out-of-bounds Read in ext4_symlink

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 13f7432bdd8e Merge branch 'bpf-tcp-listen-cb'
git tree: bpf-next
console output: https://syzkaller.appspot.com/x/log.txt?x=164fe4b4400000
kernel config: https://syzkaller.appspot.com/x/.config?x=a501a01deaf0fe9
dashboard link: https://syzkaller.appspot.com/bug?extid=3774c2af75d1aa1220af
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [adilger...@dilger.ca linux...@vger.kernel.org
linux-...@vger.kernel.org ty...@mit.edu]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3774c2...@syzkaller.appspotmail.com

==================================================================
PANIC: double fault, error_code: 0x0
BUG: KASAN: stack-out-of-bounds in memcpy include/linux/string.h:345
[inline]
BUG: KASAN: stack-out-of-bounds in ext4_symlink+0x6ea/0x1170
fs/ext4/namei.c:3156
CPU: 1 PID: 13473 Comm: syz-executor7 Not tainted 4.18.0-rc3+ #55
Read of size 24 at addr ffff8801ac37c2e0 by task syz-executor1/13506
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011

RIP: 0010:__lock_acquire+0x2e/0x5020 kernel/locking/lockdep.c:3294
CPU: 0 PID: 13506 Comm: syz-executor1 Not tainted 4.18.0-rc3+ #55
Code: 41
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
57
Call Trace:
41
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
89
cf
41
56 41
55
print_address_description+0x6c/0x20b mm/kasan/report.c:256
49
89 fd
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
41 54
check_memory_region_inline mm/kasan/kasan.c:260 [inline]
check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
45
memcpy+0x23/0x50 mm/kasan/kasan.c:302
89
memcpy include/linux/string.h:345 [inline]
ext4_symlink+0x6ea/0x1170 fs/ext4/namei.c:3156
cc 53
65
4c
8b 34
25 40
vfs_symlink+0x37a/0x5d0 fs/namei.c:4137
ee
do_symlinkat+0x242/0x2d0 fs/namei.c:4164
01 00
48
83 e4
__do_sys_symlink fs/namei.c:4183 [inline]
__se_sys_symlink fs/namei.c:4181 [inline]
__x64_sys_symlink+0x59/0x80 fs/namei.c:4181
f0 48
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
81
ec 60
03
00 00
48
8b
45
entry_SYSCALL_64_after_hwframe+0x49/0xbe
10 <89>
RIP: 0033:0x4557e7
94
Code:
24
64
80
8b
00 00
5d
00 48
00
ba 00
e9
00
14
00
fd
00
ff
00
ff
fc ff
4c
df
8b
48 89
74
84
24
24
30
98
64
RSP: 0018:ffff8801abd32ee0 EFLAGS: 00010082
c7
45
RAX: 0000000000000000 RBX: 1ffff100357a6659 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff88f92620
00
RBP: ffff8801abd33270 R08: 0000000000000000 R09: 0000000000000000
22
R10: ffff8801ac7e7be0 R11: ffff88019f3e8b7b R12: 0000000000000000
R13: ffffffff88f92620 R14: ffff88019f3e8400 R15: 0000000000000002
00 00
FS: 000000000206d940(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
00 bb
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff8801abd32ed8 CR3: 0000000199809000 CR4: 00000000001406e0
22
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
00
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
00


---
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[Dmitry Vyukov]

#syz fix: bpf: sockhash, disallow bpf_tcp_close and update in parallel

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