KASAN: use-after-free Read in search_by_entry_key

Status: auto-obsoleted due to no activity on 2026/08/19 21:55
Reported-by: syzbot+9e7dd320c1887f1d74a8@syzkaller.appspotmail.com
First crash: 125d, last: 107d
▶ ▼ Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in search_by_entry_key (2) fs 19 syz, C inconclusive inconclusive 139 943d 1536d 0/29 auto-obsoleted due to no activity on 2024/04/08 07:18
linux-4.14 KASAN: use-after-free Read in search_by_entry_key (2) reiserfs 19 syz, C error 6 1339d 1958d 0/1 upstream: reported C repro on 2021/04/16 06:17
linux-4.14 KASAN: use-after-free Read in search_by_entry_key 19 syz, C done 3 2058d 2164d 1/1 fixed on 2021/02/21 17:18
linux-4.19 KASAN: use-after-free Read in search_by_entry_key (3) reiserfs 19 syz, C error 8 1338d 1531d 0/1 upstream: reported C repro on 2022/06/17 02:59
linux-4.19 KASAN: use-after-free Read in search_by_entry_key 19 syz, C done 1 2060d 2150d 1/1 fixed on 2021/02/20 09:47
linux-5.15 KASAN: use-after-free Read in search_by_entry_key missing-backport origin:upstream 19 syz, C done 74 3d18h 1236d 0/3 upstream: reported C repro on 2023/04/08 09:36
linux-6.1 KASAN: use-after-free Read in search_by_entry_key origin:upstream missing-backport 19 syz, C inconclusive 59 132d 1221d 0/3 upstream: reported C repro on 2023/04/23 10:15
upstream KASAN: use-after-free Read in search_by_entry_key fs 19 syz, C done 3 2144d 2148d 19/29 fixed on 2021/03/10 01:49
linux-4.19 KASAN: use-after-free Read in search_by_entry_key (2) 19 syz, C done 2 1841d 1991d 1/1 fixed on 2021/09/10 21:17

Sample crash report:
REISERFS warning (device loop3): vs-13060 reiserfs_update_sd_size: stat data of object [3 6 0x0 SD] (nlink == 2) not found (pos 1)
==================================================================
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+0x59e/0xd60 fs/reiserfs/namei.c:165
Read of size 4 at addr ffff888074f69fc4 by task syz.3.621/8035

CPU: 1 PID: 8035 Comm: syz.3.621 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 bin_search_in_dir_item fs/reiserfs/namei.c:40 [inline]
 search_by_entry_key+0x59e/0xd60 fs/reiserfs/namei.c:165
 reiserfs_find_entry+0x2e9/0x1340 fs/reiserfs/namei.c:322
 reiserfs_lookup+0x1dc/0x580 fs/reiserfs/namei.c:368
 __lookup_slow+0x2a1/0x400 fs/namei.c:1702
 lookup_one_len+0x1a1/0x2e0 fs/namei.c:2752
 open_xa_dir+0x468/0x700 fs/reiserfs/xattr.c:163
 xattr_lookup+0x22/0x2a0 fs/reiserfs/xattr.c:396
 reiserfs_xattr_set_handle+0x106/0xd70 fs/reiserfs/xattr.c:535
 reiserfs_xattr_set+0x46b/0x590 fs/reiserfs/xattr.c:635
 __vfs_setxattr+0x431/0x470 fs/xattr.c:201
 __vfs_setxattr_noperm+0x12d/0x5e0 fs/xattr.c:235
 vfs_setxattr+0x16b/0x2f0 fs/xattr.c:322
 do_setxattr fs/xattr.c:630 [inline]
 path_setxattr+0x3f3/0x5d0 fs/xattr.c:659
 __do_sys_lsetxattr fs/xattr.c:684 [inline]
 __se_sys_lsetxattr fs/xattr.c:680 [inline]
 __x64_sys_lsetxattr+0xb8/0xd0 fs/xattr.c:680
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f8cabf9cdd9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8cacf24028 EFLAGS: 00000246 ORIG_RAX: 00000000000000bd
RAX: ffffffffffffffda RBX: 00007f8cac216090 RCX: 00007f8cabf9cdd9
RDX: 0000000000000000 RSI: 0000200000002080 RDI: 0000200000001180
RBP: 00007f8cac032d69 R08: 0000000000000003 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8cac216128 R14: 00007f8cac216090 R15: 00007fffe278ae08
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0001d3da40 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x74f69
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 ffffea0001d3da88 ffffea0001d3da08 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 7864, tgid 7864 (syz.4.581), ts 202455804422, free_ts 205012203221
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1581
 prep_new_page mm/page_alloc.c:1588 [inline]
 get_page_from_freelist+0x1951/0x19e0 mm/page_alloc.c:3220
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4500
 __folio_alloc+0x10/0x20 mm/page_alloc.c:4532
 vma_alloc_folio+0x47a/0x8f0 mm/mempolicy.c:2240
 shmem_alloc_folio+0x1a9/0x2a0 mm/shmem.c:1679
 shmem_alloc_and_acct_folio+0x1e6/0x6d0 mm/shmem.c:1704
 shmem_get_folio_gfp+0xcde/0x2aa0 mm/shmem.c:2041
 shmem_get_folio mm/shmem.c:2164 [inline]
 shmem_write_begin+0xf2/0x420 mm/shmem.c:2706
 generic_perform_write+0x2fe/0x5c0 mm/filemap.c:4036
 shmem_file_write_iter+0xfb/0x120 mm/shmem.c:2883
 __kernel_write_iter+0x28c/0x690 fs/read_write.c:517
 dump_emit_page fs/coredump.c:957 [inline]
 dump_user_range+0x420/0x860 fs/coredump.c:984
 elf_core_dump+0x31d0/0x3770 fs/binfmt_elf.c:2184
 do_coredump+0x17cc/0x24d0 fs/coredump.c:833
 get_signal+0x1133/0x13f0 kernel/signal.c:2888
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1181 [inline]
 free_unref_page_prepare+0x7b2/0x8c0 mm/page_alloc.c:2365
 free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2504
 release_pages+0x1f7a/0x2200 mm/swap.c:1022
 __folio_batch_release+0x71/0xe0 mm/swap.c:1042
 folio_batch_release include/linux/pagevec.h:83 [inline]
 shmem_undo_range+0x630/0x1b20 mm/shmem.c:1026
 shmem_truncate_range mm/shmem.c:1135 [inline]
 shmem_evict_inode+0x245/0x9e0 mm/shmem.c:1264
 evict+0x4ca/0x8d0 fs/inode.c:705
 __dentry_kill+0x431/0x650 fs/dcache.c:611
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xfe/0x1e0 fs/dcache.c:918
 __fput+0x5e5/0x970 fs/file_table.c:392
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x95a/0x2460 kernel/exit.c:883
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
 get_signal+0x12fc/0x13f0 kernel/signal.c:2902
 arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310

Memory state around the buggy address:
 ffff888074f69e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888074f69f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888074f69f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff888074f6a000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888074f6a080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/11 21:54 linux-6.6.y 3b9f64db0496 d168f260 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in search_by_entry_key
2026/04/23 13:45 linux-6.6.y 9760bf04666d 4c3406dc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in search_by_entry_key
* Struck through repros no longer work on HEAD.