==================================================================
BUG: KASAN: use-after-free in reiserfs_get_unused_objectid+0x1c0/0x3bc fs/reiserfs/objectid.c:87
Read of size 8188 at addr ffff0000eaac2058 by task syz.2.36/4271

CPU: 1 PID: 4271 Comm: syz.2.36 Not tainted 5.15.185-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 print_address_description+0x78/0x30c mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xec/0x15c mm/kasan/report.c:451
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x270/0x2b0 mm/kasan/generic.c:189
 memmove+0x90/0xe8 mm/kasan/shadow.c:54
 reiserfs_get_unused_objectid+0x1c0/0x3bc fs/reiserfs/objectid.c:87
 reiserfs_new_inode+0x1e0/0x133c fs/reiserfs/inode.c:1952
 reiserfs_create+0x334/0x5a8 fs/reiserfs/namei.c:668
 lookup_open fs/namei.c:3462 [inline]
 open_last_lookups fs/namei.c:3532 [inline]
 path_openat+0x1144/0x26e4 fs/namei.c:3739
 do_filp_open+0x164/0x330 fs/namei.c:3769
 do_sys_openat2+0x128/0x3d8 fs/open.c:1253
 do_sys_open fs/open.c:1269 [inline]
 __do_sys_openat fs/open.c:1285 [inline]
 __se_sys_openat fs/open.c:1280 [inline]
 __arm64_sys_openat+0x120/0x154 fs/open.c:1280
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

The buggy address belongs to the page:
page:00000000bf705422 refcount:2 mapcount:0 mapping:000000008b5518ec index:0x10 pfn:0x12aac2
memcg:ffff0000d69e4000
aops:def_blk_aops ino:700002
flags: 0x5ffc00000022036(referenced|uptodate|lru|active|private|mappedtodisk|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000022036 fffffc00037e2d88 fffffc0003ab70c8 ffff0000c049f288
raw: 0000000000000010 ffff0000e9b8dbc8 00000002ffffffff ffff0000d69e4000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000eaac2f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff0000eaac2f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff0000eaac3000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff0000eaac3080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000eaac3100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
REISERFS warning: green-16003 errcatch_is_left_mergeable: Invalid item type observed, run fsck ASAP
REISERFS warning: green-16003 errcatch_is_left_mergeable: Invalid item type observed, run fsck ASAP
REISERFS warning (device loop2): vs-13060 reiserfs_update_sd_size: stat data of object [1 2 0x0 UNKNOWN] (nlink == 1) not found (pos 2)