[syzbot] [reiserfs?] KASAN: null-ptr-deref Read in fix_nodes

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    148341f0a2f5 Merge tag 'vfs.misc.fixes.v6.3-rc6' of git://..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=131e7b5dc80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d3500b143c204867
dashboard link: https://syzkaller.appspot.com/bug?extid=5184326923f180b9d11a
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bd1a34836b5e/disk-148341f0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/04a1edfc1dd9/vmlinux-148341f0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ec7cb22838b5/bzImage-148341f0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5184326923f180b9d11a@xxxxxxxxxxxxxxxxxxxxxxxxx

REISERFS (device loop2): Remounting filesystem read-only
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:72 [inline]
BUG: KASAN: null-ptr-deref in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
BUG: KASAN: null-ptr-deref in buffer_locked include/linux/buffer_head.h:126 [inline]
BUG: KASAN: null-ptr-deref in fix_nodes+0x464/0x8660 fs/reiserfs/fix_node.c:2578
Read of size 8 at addr 0000000000000000 by task syz-executor.2/4037

CPU: 1 PID: 4037 Comm: syz-executor.2 Not tainted 6.3.0-rc5-syzkaller-00005-g148341f0a2f5 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
 print_report mm/kasan/report.c:433 [inline]
 kasan_report+0xec/0x130 mm/kasan/report.c:536
 check_region_inline mm/kasan/generic.c:181 [inline]
 kasan_check_range+0x141/0x190 mm/kasan/generic.c:187
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 buffer_locked include/linux/buffer_head.h:126 [inline]
 fix_nodes+0x464/0x8660 fs/reiserfs/fix_node.c:2578
 reiserfs_cut_from_item+0x2bd/0x1b20 fs/reiserfs/stree.c:1742
 reiserfs_do_truncate+0x630/0x1080 fs/reiserfs/stree.c:1973
 reiserfs_truncate_file+0x1b5/0x1070 fs/reiserfs/inode.c:2310
 reiserfs_setattr+0xddf/0x1370 fs/reiserfs/inode.c:3395
 notify_change+0xb2c/0x1180 fs/attr.c:482
 do_truncate+0x143/0x200 fs/open.c:66
 handle_truncate fs/namei.c:3219 [inline]
 do_open fs/namei.c:3564 [inline]
 path_openat+0x2083/0x2750 fs/namei.c:3715
 do_filp_open+0x1ba/0x410 fs/namei.c:3742
 do_sys_openat2+0x16d/0x4c0 fs/open.c:1348
 do_sys_open fs/open.c:1364 [inline]
 __do_sys_creat fs/open.c:1440 [inline]
 __se_sys_creat fs/open.c:1434 [inline]
 __x64_sys_creat+0xcd/0x120 fs/open.c:1434
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fd96be8c169
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd96cb5a168 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 00007fd96bfac1f0 RCX: 00007fd96be8c169
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000040
RBP: 00007fd96bee7ca1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffcd572849f R14: 00007fd96cb5a300 R15: 0000000000022000
 </TASK>
==================================================================


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