KASAN: use-after-free Read in leaf_paste_entries

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 13d2ce42 Linux 4.19.163
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=133aa613500000
kernel config: https://syzkaller.appspot.com/x/.config?x=fac7c3360835a4e0
dashboard link: https://syzkaller.appspot.com/bug?extid=80a7b4909b4c20c74ede
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1791eadf500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1242e41f500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+80a7b4...@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 memmove include/linux/string.h:388 [inline]
BUG: KASAN: use-after-free in leaf_paste_entries+0x417/0x910 fs/reiserfs/lbalance.c:1369
Read of size 18446744073709549059 at addr ffff88808319d9bf by task syz-executor847/8097

CPU: 0 PID: 8097 Comm: syz-executor847 Not tainted 4.19.163-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+0x1fc/0x2fe lib/dump_stack.c:118
print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
kasan_report_error.cold+0x8a/0x1c7 mm/kasan/report.c:354
kasan_report+0x8f/0x96 mm/kasan/report.c:412
memmove+0x20/0x50 mm/kasan/kasan.c:293
memmove include/linux/string.h:388 [inline]
leaf_paste_entries+0x417/0x910 fs/reiserfs/lbalance.c:1369
balance_leaf_finish_node_paste_dirent fs/reiserfs/do_balan.c:1306 [inline]
balance_leaf_finish_node_paste fs/reiserfs/do_balan.c:1332 [inline]
balance_leaf_finish_node fs/reiserfs/do_balan.c:1375 [inline]
balance_leaf+0x8fb4/0xca40 fs/reiserfs/do_balan.c:1463
do_balance+0x306/0x760 fs/reiserfs/do_balan.c:1899
reiserfs_paste_into_item+0x636/0x7d0 fs/reiserfs/stree.c:2142
reiserfs_add_entry+0x89a/0xcc0 fs/reiserfs/namei.c:566
reiserfs_mkdir+0x66e/0x980 fs/reiserfs/namei.c:858
create_privroot fs/reiserfs/xattr.c:880 [inline]
reiserfs_xattr_init+0x406/0xae0 fs/reiserfs/xattr.c:1002
reiserfs_fill_super+0x206e/0x2ce4 fs/reiserfs/super.c:2180
mount_bdev+0x2fc/0x3b0 fs/super.c:1158
mount_fs+0xa3/0x30c 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+0x113c/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+0xf9/0x620 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:00007ffe5439cba8 EFLAGS: 00000297 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffe5439cc00 RCX: 0000000000447d9a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffe5439cbc0
RBP: 00007ffe5439cbc0 R08: 00007ffe5439cc00 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000006
R13: 0000000000000004 R14: 0000000000000003 R15: 0000000000000003

The buggy address belongs to the page:
page:ffffea00020c6740 count:0 mapcount:0 mapping:0000000000000000 index:0x1
flags: 0xfff00000000000()
raw: 00fff00000000000 ffffea00020c6788 ffff8880ba02ea08 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88808319d880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88808319d900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88808319d980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88808319da00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88808319da80: 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=121d681b500000
start commit: 13d2ce42 Linux 4.19.163
git tree: linux-4.19.y

kernel config: https://syzkaller.appspot.com/x/.config?x=fac7c3360835a4e0
dashboard link: https://syzkaller.appspot.com/bug?extid=80a7b4909b4c20c74ede

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1791eadf500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1242e41f500000

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