KASAN: use-after-free Read in search_by_entry_key

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b09c3451 Linux 4.19.149
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16ff1f50500000
kernel config: https://syzkaller.appspot.com/x/.config?x=d7c6dfb55644e8fd
dashboard link: https://syzkaller.appspot.com/bug?extid=1b84cc0519f482028eca
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=162dac77900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=127f423b900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1b84cc...@syzkaller.appspotmail.com

REISERFS (device loop0): journal params: device loop0, size 15748, journal first block 18, max trans len 1024, max batch 900, max commit age 30, max trans age 30
REISERFS (device loop0): checking transaction log (loop0)
REISERFS (device loop0): Using r5 hash to sort names
REISERFS (device loop0): using 3.5.x disk format
==================================================================
BUG: KASAN: use-after-free in bin_search_in_dir_item fs/reiserfs/namei.c:40 [inline]
BUG: KASAN: use-after-free in search_by_entry_key+0xcf4/0xf50 fs/reiserfs/namei.c:164
Read of size 4 at addr ffff8880786f97bd by task syz-executor536/6501

CPU: 1 PID: 6501 Comm: syz-executor536 Not tainted 4.19.149-syzkaller #0
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+0x22c/0x33e lib/dump_stack.c:118
print_address_description.cold+0x56/0x25c mm/kasan/report.c:256
kasan_report_error.cold+0x66/0xb9 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load_n_noabort+0x8b/0xa0 mm/kasan/report.c:443
bin_search_in_dir_item fs/reiserfs/namei.c:40 [inline]
search_by_entry_key+0xcf4/0xf50 fs/reiserfs/namei.c:164
reiserfs_find_entry.part.0+0x143/0x1400 fs/reiserfs/namei.c:321
reiserfs_find_entry fs/reiserfs/namei.c:367 [inline]
reiserfs_lookup+0x24a/0x490 fs/reiserfs/namei.c:367
__lookup_slow+0x246/0x4a0 fs/namei.c:1672
lookup_one_len+0x163/0x190 fs/namei.c:2544
reiserfs_lookup_privroot+0x92/0x280 fs/reiserfs/xattr.c:963
reiserfs_fill_super+0x21e8/0x2e60 fs/reiserfs/super.c:2179
mount_bdev+0x2fc/0x3b0 fs/super.c:1158
mount_fs+0xa3/0x318 fs/super.c:1261
vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
vfs_kern_mount fs/namespace.c:951 [inline]
do_new_mount fs/namespace.c:2469 [inline]
do_mount+0x51c/0x2f10 fs/namespace.c:2799
ksys_mount+0xcf/0x130 fs/namespace.c:3015
__do_sys_mount fs/namespace.c:3029 [inline]
__se_sys_mount fs/namespace.c:3026 [inline]
__x64_sys_mount+0xba/0x150 fs/namespace.c:3026
do_syscall_64+0xf9/0x670 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x447d9a
Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 7d a3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 5a a3 fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007ffe22e07138 EFLAGS: 00000297 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffe22e07190 RCX: 0000000000447d9a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffe22e07150
RBP: 00007ffe22e07150 R08: 00007ffe22e07190 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000006
R13: 0000000000000004 R14: 0000000000000003 R15: 0000000000000003

The buggy address belongs to the page:
page:ffffea0001e1be40 count:0 mapcount:0 mapping:0000000000000000 index:0x1
flags: 0xfffe0000000000()
raw: 00fffe0000000000 ffffea0001e1be88 ffffea0001e1be08 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880786f9680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8880786f9700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880786f9780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff8880786f9800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8880786f9880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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[syzbot]

syzbot suspects this issue was fixed by commit:

commit b8590c82b3ccf9fb4d9f0b0b097be10736869333
Author: Rustam Kovhaev <rkov...@gmail.com>
Date: Sun Nov 1 14:09:58 2020 +0000

reiserfs: add check for an invalid ih_entry_count

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14d93d12d00000
start commit: b09c3451 Linux 4.19.149
git tree: linux-4.19.y

kernel config: https://syzkaller.appspot.com/x/.config?x=d7c6dfb55644e8fd
dashboard link: https://syzkaller.appspot.com/bug?extid=1b84cc0519f482028eca

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=162dac77900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=127f423b900000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: reiserfs: add check for an invalid ih_entry_count

For information about bisection process see: https://goo.gl/tpsmEJ#bisection