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KASAN: use-after-free Read in ext4_inlinedir_to_tree

Status: upstream: reported C repro on 2024/04/14 03:44
Reported-by: syzbot+52813a2561e5222492ee@syzkaller.appspotmail.com
First crash: 689d, last: 9d02h
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in ext4_inlinedir_to_tree ext4 19 C done error 6 60d 552d 0/29 upstream: reported C repro on 2024/08/28 22:55
android-5-15 KASAN: use-after-free Read in ext4_inlinedir_to_tree origin:upstream 19 C 6 17d 38d 0/2 upstream: reported C repro on 2026/01/25 06:15
android-54 KASAN: slab-out-of-bounds Read in ext4_inlinedir_to_tree 17 C 1 324d 689d 0/2 upstream: reported C repro on 2024/04/14 03:10
upstream KMSAN: uninit-value in number (4) kernel 7 C 7189 1197d 1575d 0/29 closed as invalid on 2022/11/28 10:01
android-6-1 KASAN: slab-out-of-bounds Read in ext4_inlinedir_to_tree origin:upstream 17 C error 1 8d17h 689d 0/2 upstream: reported C repro on 2024/04/14 08:35
upstream KMSAN: uninit-value in ext4_inlinedir_to_tree ext4 7 C 267 627d 673d 27/29 fixed on 2024/08/14 03:44
upstream KMSAN: uninit-value in htree_dirblock_to_tree ext4 7 204 1025d 1155d 22/29 fixed on 2023/07/01 16:05
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/02/23 06:36 8m retest repro android13-5.10-lts report log
2026/02/23 06:36 5m retest repro android13-5.10-lts report log
2026/02/07 20:49 9m retest repro android13-5.10-lts report log
2025/12/17 22:50 32m retest repro android13-5.10-lts report log
2025/10/08 17:45 8m retest repro android13-5.10-lts report log
2025/07/28 22:27 12m retest repro android13-5.10-lts report log
2025/05/19 11:42 5m retest repro android13-5.10-lts report log
2025/03/10 07:13 10m retest repro android13-5.10-lts report log
2024/12/30 04:53 5m retest repro android13-5.10-lts report log
2024/10/20 00:19 15m retest repro android13-5.10-lts report log

Sample crash report:
EXT4-fs (loop4): mounted filesystem without journal. Opts: errors=remount-ro,
EXT4-fs error (device loop4): ext4_validate_block_bitmap:438: comm syz.4.21: bg 0: block 465: padding at end of block bitmap is not set
EXT4-fs (loop4): Remounting filesystem read-only
==================================================================
BUG: KASAN: use-after-free in ext4_read_inline_data fs/ext4/inline.c:209 [inline]
BUG: KASAN: use-after-free in ext4_inlinedir_to_tree+0x5f6/0xfd0 fs/ext4/inline.c:1419
Read of size 52 at addr ffff888112920b97 by task syz.4.21/380

CPU: 1 PID: 380 Comm: syz.4.21 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0xe2/0x130 mm/kasan/report.c:452
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x249/0x2a0 mm/kasan/generic.c:189
 memcpy+0x2d/0x70 mm/kasan/shadow.c:65
 ext4_read_inline_data fs/ext4/inline.c:209 [inline]
 ext4_inlinedir_to_tree+0x5f6/0xfd0 fs/ext4/inline.c:1419
 ext4_htree_fill_tree+0x508/0x1160 fs/ext4/namei.c:1186
 ext4_dx_readdir fs/ext4/dir.c:601 [inline]
 ext4_readdir+0x2c49/0x3ab0 fs/ext4/dir.c:145
 iterate_dir+0x260/0x570 fs/readdir.c:-1
 __do_sys_getdents fs/readdir.c:286 [inline]
 __se_sys_getdents+0xf2/0x250 fs/readdir.c:271
 __x64_sys_getdents+0x7b/0x90 fs/readdir.c:271
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f6de8b88eb9
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:00007ffe6e5885f8 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007f6de8e03fa0 RCX: 00007f6de8b88eb9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007f6de8bf6c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6de8e03fac R14: 00007f6de8e03fa0 R15: 00007f6de8e03fa0

Allocated by task 109:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 __kasan_slab_alloc+0xbd/0xf0 mm/kasan/common.c:463
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x162/0x2d0 mm/slub.c:2965
 kmem_cache_zalloc include/linux/slab.h:657 [inline]
 __alloc_file+0x28/0x320 fs/file_table.c:101
 alloc_empty_file+0x97/0x180 fs/file_table.c:151
 path_openat+0xf5/0x31c0 fs/namei.c:3503
 do_filp_open+0x1e2/0x410 fs/namei.c:3544
 do_sys_openat2+0x19f/0x750 fs/open.c:1219
 do_sys_open fs/open.c:1235 [inline]
 __do_sys_openat fs/open.c:1251 [inline]
 __se_sys_openat fs/open.c:1246 [inline]
 __x64_sys_openat+0x136/0x160 fs/open.c:1246
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 107:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kmem_cache_free+0x100/0x2d0 mm/slub.c:3224
 file_free_rcu+0x93/0xa0 fs/file_table.c:50
 rcu_do_batch+0x4ef/0xab0 kernel/rcu/tree.c:2494
 rcu_core+0x577/0xd80 kernel/rcu/tree.c:2735
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2748
 __do_softirq+0x255/0x563 kernel/softirq.c:309

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu kernel/rcu/tree.c:2980 [inline]
 call_rcu+0x11a/0x10b0 kernel/rcu/tree.c:3054
 file_free fs/file_table.c:58 [inline]
 __fput+0x5ad/0x770 fs/file_table.c:299
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Second to last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack+0xe/0x10 mm/kasan/generic.c:353
 task_work_add+0x27/0x1e0 kernel/task_work.c:38
 fput_many+0xe7/0x1a0 fs/file_table.c:342
 fput+0x1a/0x20 fs/file_table.c:358
 filp_close+0x105/0x150 fs/open.c:1335
 __close_fd+0x35/0x50 fs/file.c:702
 __do_sys_close fs/open.c:1348 [inline]
 __se_sys_close fs/open.c:1346 [inline]
 __x64_sys_close+0x66/0xb0 fs/open.c:1346
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff888112920a80
 which belongs to the cache filp of size 296
The buggy address is located 279 bytes inside of
 296-byte region [ffff888112920a80, ffff888112920ba8)
The buggy address belongs to the page:
page:ffffea00044a4800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x112920
head:ffffea00044a4800 order:1 compound_mapcount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff88810018a300
raw: 0000000000000000 0000000000150015 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 109, ts 4399463705, free_ts 0
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x223b/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x290/0x620 mm/page_alloc.c:5370
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2a6/0x450 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x1ac/0x2d0 mm/slub.c:2965
 kmem_cache_zalloc include/linux/slab.h:657 [inline]
 __alloc_file+0x28/0x320 fs/file_table.c:101
 alloc_empty_file+0x97/0x180 fs/file_table.c:151
 path_openat+0xf5/0x31c0 fs/namei.c:3503
 do_filp_open+0x1e2/0x410 fs/namei.c:3544
 do_sys_openat2+0x19f/0x750 fs/open.c:1219
 do_sys_open fs/open.c:1235 [inline]
 __do_sys_openat fs/open.c:1251 [inline]
 __se_sys_openat fs/open.c:1246 [inline]
 __x64_sys_openat+0x136/0x160 fs/open.c:1246
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888112920a80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888112920b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888112920b80: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc
                         ^
 ffff888112920c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888112920c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
EXT4-fs error (device loop4): ext4_inlinedir_to_tree:1457: inode #12: block 7: comm syz.4.21: path /0/file1/file0: bad entry in directory: rec_len % 4 != 0 - offset=35110, inode=3517778242, rec_len=35106, size=112 fake=0

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/09 03:34 android13-5.10-lts 58c592510fcd 4c131dc4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci2-android-5-10 KASAN: use-after-free Read in ext4_inlinedir_to_tree
2026/01/24 05:26 android13-5.10-lts 5601baec60aa 4f25b9b4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci2-android-5-10 KASAN: use-after-free Read in ext4_inlinedir_to_tree
2024/04/14 03:43 android13-5.10-lts 4e1bc8d8e8ae c8349e48 .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2] ci2-android-5-10 KASAN: use-after-free Read in ext4_inlinedir_to_tree
2026/02/09 02:23 android13-5.10-lts 58c592510fcd 4c131dc4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci2-android-5-10 KASAN: slab-out-of-bounds Read in ext4_inlinedir_to_tree
2026/01/24 16:05 android13-5.10-lts 5601baec60aa 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in ext4_inlinedir_to_tree
2026/01/24 04:53 android13-5.10-lts 5601baec60aa 4f25b9b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in ext4_inlinedir_to_tree
2026/01/24 04:53 android13-5.10-lts 5601baec60aa 4f25b9b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in ext4_inlinedir_to_tree
2026/01/24 16:06 android13-5.10-lts 5601baec60aa 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: slab-out-of-bounds Read in ext4_inlinedir_to_tree
2026/01/24 16:06 android13-5.10-lts 5601baec60aa 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: slab-out-of-bounds Read in ext4_inlinedir_to_tree
* Struck through repros no longer work on HEAD.