==================================================================
BUG: KASAN: use-after-free in reiserfs_get_unused_objectid+0x1c0/0x3bc fs/reiserfs/objectid.c:87
Read of size 8188 at addr ffff0000f6d06058 by task syz.3.75/4750

CPU: 1 PID: 4750 Comm: syz.3.75 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/26/2026
Call trace:
 dump_backtrace+0x1c0/0x1ec arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0xfc mm/kasan/report.c:524
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x258/0x290 mm/kasan/generic.c:189
 memmove+0x48/0x90 mm/kasan/shadow.c:54
 reiserfs_get_unused_objectid+0x1c0/0x3bc fs/reiserfs/objectid.c:87
 reiserfs_new_inode+0x1f8/0x13ac fs/reiserfs/inode.c:1944
 reiserfs_create+0x350/0x5d8 fs/reiserfs/namei.c:668
 lookup_open fs/namei.c:3490 [inline]
 open_last_lookups fs/namei.c:3558 [inline]
 path_openat+0xe18/0x26bc fs/namei.c:3788
 do_filp_open+0x194/0x384 fs/namei.c:3818
 do_sys_openat2+0x134/0x3f4 fs/open.c:1320
 do_sys_open fs/open.c:1336 [inline]
 __do_sys_openat fs/open.c:1352 [inline]
 __se_sys_openat fs/open.c:1347 [inline]
 __arm64_sys_openat+0x118/0x14c fs/open.c:1347
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the physical page:
page:00000000fd05d1d1 refcount:2 mapcount:0 mapping:00000000a9fee627 index:0x10 pfn:0x136d06
memcg:ffff0000c407a000
aops:def_blk_aops ino:700003
flags: 0x5ffd60000022056(referenced|uptodate|lru|workingset|private|mappedtodisk|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffd60000022056 fffffc0003e4a088 fffffc0003d9cdc8 ffff0000c0496b10
raw: 0000000000000010 ffff0000e0e50ae0 00000002ffffffff ffff0000c407a000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000f6d07f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff0000f6d07f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff0000f6d08000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff0000f6d08080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000f6d08100: 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 loop3): vs-13060 reiserfs_update_sd_size: stat data of object [1 2 0x0 UNKNOWN] (nlink == 1) not found (pos 2)