* Re: [syzbot ci] Re: Data in direntry (dirdata) feature
2026-04-18 6:47 ` [syzbot ci] Re: Data in direntry (dirdata) feature syzbot ci
@ 2026-04-22 9:34 ` Artem Blagodarenko
2026-04-22 10:09 ` syzbot ci
0 siblings, 1 reply; 3+ messages in thread
From: Artem Blagodarenko @ 2026-04-22 9:34 UTC (permalink / raw)
To: syzbot ci; +Cc: syzbot@lists.linux.dev
[-- Attachment #1.1: Type: text/plain, Size: 42587 bytes --]
#syz test
From: syzbot ci <syzbot+ci6167b51351f50705@syzkaller.appspotmail.com>
Date: Saturday, 18 April 2026 at 07:47
To: adilger.kernel@dilger.ca <adilger.kernel@dilger.ca>, adilger@dilger.ca <adilger@dilger.ca>, artem.blagodarenko@gmail.com <artem.blagodarenko@gmail.com>, linux-ext4@vger.kernel.org <linux-ext4@vger.kernel.org>, pravin.shelar@sun.com <pravin.shelar@sun.com>
Cc: syzbot@lists.linux.dev <syzbot@lists.linux.dev>, syzkaller-bugs@googlegroups.com <syzkaller-bugs@googlegroups.com>
Subject: [syzbot ci] Re: Data in direntry (dirdata) feature
syzbot ci has tested the following series
[v1] Data in direntry (dirdata) feature
https://lore.kernel.org/all/20260417213723.74204-1-artem.blagodarenko@gmail.com
* [PATCH 1/3] ext4: make dirdata work with metadata_csum
* [PATCH 2/3] ext4: add dirdata support structures and helpers
* [PATCH 3/3] ext4: dirdata feature
and found the following issues:
* KASAN: slab-out-of-bounds Read in __ext4_check_dir_entry
* KASAN: slab-out-of-bounds Read in dx_probe
* KASAN: slab-use-after-free Read in __ext4_check_dir_entry
* KASAN: slab-use-after-free Read in dx_probe
* KASAN: use-after-free Read in __ext4_check_dir_entry
Full report is available here:
https://ci.syzbot.org/series/590e846e-42c0-4497-b6ae-b95ed4468941
***
KASAN: slab-out-of-bounds Read in __ext4_check_dir_entry
tree: torvalds
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
base: 70b672833f4025341c11b22c7f83778a5cd611bc
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/7b860156-1ca9-441f-b899-ebfb5a09620d/config
syz repro: https://ci.syzbot.org/findings/d27eccd2-4663-4047-abb9-9c24cb32f887/syz_repro
loop0: lost filesystem error report for type 5 error -117
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
==================================================================
BUG: KASAN: slab-out-of-bounds in ext4_dirent_get_data_len fs/ext4/ext4.h:4040 [inline]
BUG: KASAN: slab-out-of-bounds in ext4_dir_entry_len fs/ext4/ext4.h:4060 [inline]
BUG: KASAN: slab-out-of-bounds in __ext4_check_dir_entry+0x527/0xa70 fs/ext4/dir.c:96
Read of size 1 at addr ffff8881090bfe5c by task syz.0.20/5967
CPU: 1 UID: 0 PID: 5967 Comm: syz.0.20 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xba/0x230 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
ext4_dirent_get_data_len fs/ext4/ext4.h:4040 [inline]
ext4_dir_entry_len fs/ext4/ext4.h:4060 [inline]
__ext4_check_dir_entry+0x527/0xa70 fs/ext4/dir.c:96
ext4_inlinedir_to_tree+0x6be/0xbf0 fs/ext4/inline.c:1322
ext4_htree_fill_tree+0x50b/0x1230 fs/ext4/namei.c:1184
ext4_dx_readdir fs/ext4/dir.c:600 [inline]
ext4_readdir+0x2f7b/0x3870 fs/ext4/dir.c:146
iterate_dir+0x399/0x570 fs/readdir.c:108
__do_sys_getdents64 fs/readdir.c:412 [inline]
__se_sys_getdents64+0xf1/0x280 fs/readdir.c:397
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe47219c819
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:00007fe4730c0028 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007fe472415fa0 RCX: 00007fe47219c819
RDX: 000000000000ff80 RSI: 9999999999999999 RDI: 0000000000000004
RBP: 00007fe472232c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe472416038 R14: 00007fe472415fa0 R15: 00007ffff595c618
</TASK>
Allocated by task 5967:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__do_kmalloc_node mm/slub.c:5260 [inline]
__kmalloc_noprof+0x35c/0x760 mm/slub.c:5272
kmalloc_noprof include/linux/slab.h:954 [inline]
ext4_mb_init+0x15d/0x2ad0 fs/ext4/mballoc.c:3729
__ext4_fill_super fs/ext4/super.c:5623 [inline]
ext4_fill_super+0x5647/0x6320 fs/ext4/super.c:5793
get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
vfs_get_tree+0x92/0x2a0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3763 [inline]
do_new_mount+0x341/0xd30 fs/namespace.c:3839
do_mount fs/namespace.c:4172 [inline]
__do_sys_mount fs/namespace.c:4361 [inline]
__se_sys_mount+0x31d/0x420 fs/namespace.c:4338
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff8881090bfe00
which belongs to the cache kmalloc-64 of size 64
The buggy address is located 44 bytes to the right of
allocated 48-byte region [ffff8881090bfe00, ffff8881090bfe30)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1090bf
flags: 0x17ff00000000000(node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 017ff00000000000 ffff8881000418c0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800200020 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 16414655371, free_ts 15537272896
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
prep_new_page mm/page_alloc.c:1897 [inline]
get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
alloc_slab_page mm/slub.c:3292 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3481
new_slab mm/slub.c:3539 [inline]
refill_objects+0x331/0x3c0 mm/slub.c:7175
refill_sheaf mm/slub.c:2812 [inline]
__pcs_replace_empty_main+0x2e6/0x730 mm/slub.c:4615
alloc_from_pcs mm/slub.c:4717 [inline]
slab_alloc_node mm/slub.c:4851 [inline]
__do_kmalloc_node mm/slub.c:5259 [inline]
__kmalloc_noprof+0x474/0x760 mm/slub.c:5272
kmalloc_noprof include/linux/slab.h:954 [inline]
kzalloc_noprof include/linux/slab.h:1188 [inline]
kobject_get_path+0xc5/0x2f0 lib/kobject.c:161
kobject_uevent_env+0x2a1/0x9e0 lib/kobject_uevent.c:545
really_probe+0x789/0xaf0 drivers/base/dd.c:771
__driver_probe_device+0x18c/0x320 drivers/base/dd.c:863
driver_probe_device+0x4f/0x240 drivers/base/dd.c:893
__device_attach_driver+0x279/0x430 drivers/base/dd.c:1021
bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500
__device_attach+0x2c5/0x450 drivers/base/dd.c:1093
device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1148
page last free pid 33 tgid 33 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1433 [inline]
__free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
vfree+0x25a/0x400 mm/vmalloc.c:3479
delayed_vfree_work+0x55/0x80 mm/vmalloc.c:3398
process_one_work kernel/workqueue.c:3276 [inline]
process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Memory state around the buggy address:
ffff8881090bfd00: 00 00 00 00 00 00 00 04 fc fc fc fc fc fc fc fc
ffff8881090bfd80: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>ffff8881090bfe00: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
^
ffff8881090bfe80: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8881090bff00: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
==================================================================
***
KASAN: slab-out-of-bounds Read in dx_probe
tree: torvalds
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
base: 70b672833f4025341c11b22c7f83778a5cd611bc
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/7b860156-1ca9-441f-b899-ebfb5a09620d/config
syz repro: https://ci.syzbot.org/findings/a5fcf3bd-f1ae-4b81-b5d2-f96899ea7690/syz_repro
==================================================================
BUG: KASAN: slab-out-of-bounds in ext4_dir_entry_is_tail fs/ext4/ext4.h:4001 [inline]
BUG: KASAN: slab-out-of-bounds in ext4_dirent_get_data_len fs/ext4/ext4.h:4024 [inline]
BUG: KASAN: slab-out-of-bounds in ext4_dir_entry_len fs/ext4/ext4.h:4060 [inline]
BUG: KASAN: slab-out-of-bounds in dx_root_limit fs/ext4/namei.c:583 [inline]
BUG: KASAN: slab-out-of-bounds in dx_probe+0x1ac9/0x1d90 fs/ext4/namei.c:861
Read of size 4 at addr ffff88816a408c10 by task syz.2.19/5980
CPU: 1 UID: 0 PID: 5980 Comm: syz.2.19 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xba/0x230 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
ext4_dir_entry_is_tail fs/ext4/ext4.h:4001 [inline]
ext4_dirent_get_data_len fs/ext4/ext4.h:4024 [inline]
ext4_dir_entry_len fs/ext4/ext4.h:4060 [inline]
dx_root_limit fs/ext4/namei.c:583 [inline]
dx_probe+0x1ac9/0x1d90 fs/ext4/namei.c:861
ext4_dx_find_entry fs/ext4/namei.c:1812 [inline]
__ext4_find_entry+0x5a9/0x2140 fs/ext4/namei.c:1652
ext4_lookup_entry fs/ext4/namei.c:1794 [inline]
ext4_lookup+0x17b/0x710 fs/ext4/namei.c:1860
__lookup_slow+0x2b7/0x410 fs/namei.c:1916
lookup_slow+0x53/0x70 fs/namei.c:1933
walk_component fs/namei.c:2279 [inline]
lookup_last fs/namei.c:2780 [inline]
path_lookupat+0x3f5/0x8c0 fs/namei.c:2804
filename_lookup+0x256/0x5d0 fs/namei.c:2833
user_path_at+0x40/0x160 fs/namei.c:3612
do_mount fs/namespace.c:4169 [inline]
__do_sys_mount fs/namespace.c:4361 [inline]
__se_sys_mount+0x2dc/0x420 fs/namespace.c:4338
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f518919c819
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:00007f5189fbb028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f5189415fa0 RCX: 00007f518919c819
RDX: 0000200000000140 RSI: 0000200000000100 RDI: 0000000000000000
RBP: 00007f5189232c91 R08: 0000200000000d80 R09: 0000000000000000
R10: 0000000001302060 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5189416038 R14: 00007f5189415fa0 R15: 00007ffc5d8d15b8
</TASK>
Allocated by task 5243:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__do_kmalloc_node mm/slub.c:5260 [inline]
__kvmalloc_node_noprof+0x528/0x8a0 mm/slub.c:6752
evdev_open+0xeb/0x5b0 drivers/input/evdev.c:468
chrdev_open+0x4cd/0x5e0 fs/char_dev.c:411
do_dentry_open+0x785/0x14e0 fs/open.c:949
vfs_open+0x3b/0x340 fs/open.c:1081
do_open fs/namei.c:4671 [inline]
path_openat+0x2e08/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 fs/open.c:1366
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff88816a408000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1088 bytes to the right of
allocated 2000-byte region [ffff88816a408000, ffff88816a4087d0)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x16a408
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000040 ffff888100042000 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000
head: 057ff00000000040 ffff888100042000 dead000000000100 dead000000000122
head: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000
head: 057ff00000000003 ffffea0005a90201 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5243, tgid 5243 (acpid), ts 25906150911, free_ts 21905842969
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
prep_new_page mm/page_alloc.c:1897 [inline]
get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
alloc_slab_page mm/slub.c:3292 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3481
new_slab mm/slub.c:3539 [inline]
refill_objects+0x331/0x3c0 mm/slub.c:7175
refill_sheaf mm/slub.c:2812 [inline]
__pcs_replace_empty_main+0x2e6/0x730 mm/slub.c:4615
alloc_from_pcs mm/slub.c:4717 [inline]
slab_alloc_node mm/slub.c:4851 [inline]
__do_kmalloc_node mm/slub.c:5259 [inline]
__kvmalloc_node_noprof+0x657/0x8a0 mm/slub.c:6752
evdev_open+0xeb/0x5b0 drivers/input/evdev.c:468
chrdev_open+0x4cd/0x5e0 fs/char_dev.c:411
do_dentry_open+0x785/0x14e0 fs/open.c:949
vfs_open+0x3b/0x340 fs/open.c:1081
do_open fs/namei.c:4671 [inline]
path_openat+0x2e08/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 fs/open.c:1366
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
page last free pid 9 tgid 9 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1433 [inline]
__free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
vfree+0x25a/0x400 mm/vmalloc.c:3479
delayed_vfree_work+0x55/0x80 mm/vmalloc.c:3398
process_one_work kernel/workqueue.c:3276 [inline]
process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Memory state around the buggy address:
ffff88816a408b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88816a408b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88816a408c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff88816a408c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88816a408d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
***
KASAN: slab-use-after-free Read in __ext4_check_dir_entry
tree: torvalds
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
base: 70b672833f4025341c11b22c7f83778a5cd611bc
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/7b860156-1ca9-441f-b899-ebfb5a09620d/config
syz repro: https://ci.syzbot.org/findings/e493ff66-4032-4979-9b5d-5118b2768ca5/syz_repro
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
==================================================================
BUG: KASAN: slab-use-after-free in ext4_dirent_get_data_len fs/ext4/ext4.h:4040 [inline]
BUG: KASAN: slab-use-after-free in ext4_dir_entry_len fs/ext4/ext4.h:4060 [inline]
BUG: KASAN: slab-use-after-free in __ext4_check_dir_entry+0x527/0xa70 fs/ext4/dir.c:96
Read of size 1 at addr ffff88810138889c by task syz.0.24/5978
CPU: 0 UID: 0 PID: 5978 Comm: syz.0.24 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xba/0x230 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
ext4_dirent_get_data_len fs/ext4/ext4.h:4040 [inline]
ext4_dir_entry_len fs/ext4/ext4.h:4060 [inline]
__ext4_check_dir_entry+0x527/0xa70 fs/ext4/dir.c:96
ext4_inlinedir_to_tree+0x6be/0xbf0 fs/ext4/inline.c:1322
ext4_htree_fill_tree+0x50b/0x1230 fs/ext4/namei.c:1184
ext4_dx_readdir fs/ext4/dir.c:600 [inline]
ext4_readdir+0x2f7b/0x3870 fs/ext4/dir.c:146
iterate_dir+0x399/0x570 fs/readdir.c:108
__do_sys_getdents64 fs/readdir.c:412 [inline]
__se_sys_getdents64+0xf1/0x280 fs/readdir.c:397
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff3fe19c819
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:00007ff3fefac028 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007ff3fe415fa0 RCX: 00007ff3fe19c819
RDX: 000000000000ff80 RSI: 9999999999999999 RDI: 0000000000000004
RBP: 00007ff3fe232c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff3fe416038 R14: 00007ff3fe415fa0 R15: 00007ffd39a74998
</TASK>
Allocated by task 5766:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__do_kmalloc_node mm/slub.c:5260 [inline]
__kmalloc_noprof+0x35c/0x760 mm/slub.c:5272
kmalloc_noprof include/linux/slab.h:954 [inline]
kzalloc_noprof include/linux/slab.h:1188 [inline]
tomoyo_encode2 security/tomoyo/realpath.c:45 [inline]
tomoyo_encode+0x28b/0x550 security/tomoyo/realpath.c:80
tomoyo_realpath_from_path+0x58d/0x5d0 security/tomoyo/realpath.c:283
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_check_open_permission+0x229/0x470 security/tomoyo/file.c:776
security_file_open+0xa9/0x240 security/security.c:2637
do_dentry_open+0x384/0x14e0 fs/open.c:926
vfs_open+0x3b/0x340 fs/open.c:1081
do_open fs/namei.c:4671 [inline]
path_openat+0x2e08/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 fs/open.c:1366
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 5766:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2685 [inline]
slab_free mm/slub.c:6165 [inline]
kfree+0x1c1/0x630 mm/slub.c:6483
tomoyo_check_open_permission+0x32c/0x470 security/tomoyo/file.c:791
security_file_open+0xa9/0x240 security/security.c:2637
do_dentry_open+0x384/0x14e0 fs/open.c:926
vfs_open+0x3b/0x340 fs/open.c:1081
do_open fs/namei.c:4671 [inline]
path_openat+0x2e08/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 fs/open.c:1366
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff888101388880
which belongs to the cache kmalloc-64 of size 64
The buggy address is located 28 bytes inside of
freed 64-byte region [ffff888101388880, ffff8881013888c0)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x101388
flags: 0x17ff00000000000(node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 017ff00000000000 ffff8881000418c0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800200020 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 26, tgid 26 (kworker/u9:0), ts 4100832473, free_ts 4100767003
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
prep_new_page mm/page_alloc.c:1897 [inline]
get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
alloc_slab_page mm/slub.c:3292 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3481
new_slab mm/slub.c:3539 [inline]
refill_objects+0x331/0x3c0 mm/slub.c:7175
refill_sheaf mm/slub.c:2812 [inline]
alloc_full_sheaf mm/slub.c:2834 [inline]
__pcs_replace_empty_main+0x40a/0x730 mm/slub.c:4626
alloc_from_pcs mm/slub.c:4717 [inline]
slab_alloc_node mm/slub.c:4851 [inline]
__do_kmalloc_node mm/slub.c:5259 [inline]
__kmalloc_noprof+0x474/0x760 mm/slub.c:5272
kmalloc_noprof include/linux/slab.h:954 [inline]
kzalloc_noprof include/linux/slab.h:1188 [inline]
lsm_blob_alloc security/security.c:193 [inline]
lsm_task_alloc security/security.c:245 [inline]
security_task_alloc+0x4d/0x330 security/security.c:2683
copy_process+0x16df/0x3cd0 kernel/fork.c:2206
kernel_clone+0x248/0x8e0 kernel/fork.c:2658
user_mode_thread+0x110/0x180 kernel/fork.c:2734
call_usermodehelper_exec_work+0x5c/0x230 kernel/umh.c:171
process_one_work kernel/workqueue.c:3276 [inline]
process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
page last free pid 26 tgid 26 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1433 [inline]
__free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
__kasan_populate_vmalloc_do mm/kasan/shadow.c:393 [inline]
__kasan_populate_vmalloc+0x1b2/0x1d0 mm/kasan/shadow.c:424
kasan_populate_vmalloc include/linux/kasan.h:580 [inline]
alloc_vmap_area+0xd73/0x14b0 mm/vmalloc.c:2129
__get_vm_area_node+0x1f8/0x300 mm/vmalloc.c:3232
__vmalloc_node_range_noprof+0x372/0x1730 mm/vmalloc.c:4024
__vmalloc_node_noprof+0xc2/0x100 mm/vmalloc.c:4124
alloc_thread_stack_node kernel/fork.c:355 [inline]
dup_task_struct+0x292/0x9e0 kernel/fork.c:924
copy_process+0x508/0x3cd0 kernel/fork.c:2051
kernel_clone+0x248/0x8e0 kernel/fork.c:2658
user_mode_thread+0x110/0x180 kernel/fork.c:2734
call_usermodehelper_exec_work+0x5c/0x230 kernel/umh.c:171
process_one_work kernel/workqueue.c:3276 [inline]
process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Memory state around the buggy address:
ffff888101388780: 00 00 00 00 00 00 00 04 fc fc fc fc fc fc fc fc
ffff888101388800: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff888101388880: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
^
ffff888101388900: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc
ffff888101388980: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
==================================================================
***
KASAN: slab-use-after-free Read in dx_probe
tree: torvalds
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
base: 70b672833f4025341c11b22c7f83778a5cd611bc
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/7b860156-1ca9-441f-b899-ebfb5a09620d/config
syz repro: https://ci.syzbot.org/findings/5524eff5-62fb-4cff-8d4e-7e3750aa921b/syz_repro
EXT4-fs (loop2): mounted filesystem 00000000-0000-0000-0000-000000000000 ro without journal. Quota mode: none.
==================================================================
BUG: KASAN: slab-use-after-free in ext4_dir_entry_is_tail fs/ext4/ext4.h:4001 [inline]
BUG: KASAN: slab-use-after-free in ext4_dirent_get_data_len fs/ext4/ext4.h:4024 [inline]
BUG: KASAN: slab-use-after-free in ext4_dir_entry_len fs/ext4/ext4.h:4060 [inline]
BUG: KASAN: slab-use-after-free in dx_root_limit fs/ext4/namei.c:583 [inline]
BUG: KASAN: slab-use-after-free in dx_probe+0x1ac9/0x1d90 fs/ext4/namei.c:861
Read of size 4 at addr ffff888109c42c10 by task syz.2.20/5984
CPU: 0 UID: 0 PID: 5984 Comm: syz.2.20 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xba/0x230 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
ext4_dir_entry_is_tail fs/ext4/ext4.h:4001 [inline]
ext4_dirent_get_data_len fs/ext4/ext4.h:4024 [inline]
ext4_dir_entry_len fs/ext4/ext4.h:4060 [inline]
dx_root_limit fs/ext4/namei.c:583 [inline]
dx_probe+0x1ac9/0x1d90 fs/ext4/namei.c:861
ext4_dx_find_entry fs/ext4/namei.c:1812 [inline]
__ext4_find_entry+0x5a9/0x2140 fs/ext4/namei.c:1652
ext4_lookup_entry fs/ext4/namei.c:1794 [inline]
ext4_lookup+0x17b/0x710 fs/ext4/namei.c:1860
lookup_open fs/namei.c:4456 [inline]
open_last_lookups fs/namei.c:4583 [inline]
path_openat+0x11ac/0x3860 fs/namei.c:4827
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 fs/open.c:1366
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb97dd9c819
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:00007fb97ec96028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fb97e015fa0 RCX: 00007fb97dd9c819
RDX: 0000000000042041 RSI: 0000200000000700 RDI: ffffffffffffff9c
RBP: 00007fb97de32c91 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000001d R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb97e016038 R14: 00007fb97e015fa0 R15: 00007fffcac5f5a8
</TASK>
Allocated by task 5828:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__do_kmalloc_node mm/slub.c:5260 [inline]
__kmalloc_noprof+0x35c/0x760 mm/slub.c:5272
kmalloc_noprof include/linux/slab.h:954 [inline]
tomoyo_realpath_from_path+0xe3/0x5d0 security/tomoyo/realpath.c:251
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x283/0x560 security/tomoyo/file.c:827
tomoyo_path_symlink+0xab/0xf0 security/tomoyo/tomoyo.c:212
security_path_symlink+0x16f/0x360 security/security.c:1477
filename_symlinkat+0x134/0x410 fs/namei.c:5638
__do_sys_symlink fs/namei.c:5667 [inline]
__se_sys_symlink+0x4d/0x2b0 fs/namei.c:5663
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 5828:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2685 [inline]
slab_free mm/slub.c:6165 [inline]
kfree+0x1c1/0x630 mm/slub.c:6483
tomoyo_realpath_from_path+0x598/0x5d0 security/tomoyo/realpath.c:286
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x283/0x560 security/tomoyo/file.c:827
tomoyo_path_symlink+0xab/0xf0 security/tomoyo/tomoyo.c:212
security_path_symlink+0x16f/0x360 security/security.c:1477
filename_symlinkat+0x134/0x410 fs/namei.c:5638
__do_sys_symlink fs/namei.c:5667 [inline]
__se_sys_symlink+0x4d/0x2b0 fs/namei.c:5663
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff888109c42000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 3088 bytes inside of
freed 4096-byte region [ffff888109c42000, ffff888109c43000)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x109c40
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x17ff00000000040(head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 017ff00000000040 ffff888100042140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
head: 017ff00000000040 ffff888100042140 dead000000000100 dead000000000122
head: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
head: 017ff00000000003 ffffea0004271001 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5828, tgid 5828 (udevd), ts 67573015608, free_ts 47549723112
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
prep_new_page mm/page_alloc.c:1897 [inline]
get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
alloc_slab_page mm/slub.c:3292 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3481
new_slab mm/slub.c:3539 [inline]
refill_objects+0x331/0x3c0 mm/slub.c:7175
refill_sheaf mm/slub.c:2812 [inline]
__pcs_replace_empty_main+0x2e6/0x730 mm/slub.c:4615
alloc_from_pcs mm/slub.c:4717 [inline]
slab_alloc_node mm/slub.c:4851 [inline]
__do_kmalloc_node mm/slub.c:5259 [inline]
__kmalloc_noprof+0x474/0x760 mm/slub.c:5272
kmalloc_noprof include/linux/slab.h:954 [inline]
tomoyo_realpath_from_path+0xe3/0x5d0 security/tomoyo/realpath.c:251
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x283/0x560 security/tomoyo/file.c:827
tomoyo_path_symlink+0xab/0xf0 security/tomoyo/tomoyo.c:212
security_path_symlink+0x16f/0x360 security/security.c:1477
filename_symlinkat+0x134/0x410 fs/namei.c:5638
__do_sys_symlink fs/namei.c:5667 [inline]
__se_sys_symlink+0x4d/0x2b0 fs/namei.c:5663
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5718 tgid 5718 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1433 [inline]
__free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
__slab_free+0x263/0x2b0 mm/slub.c:5573
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4538 [inline]
slab_alloc_node mm/slub.c:4866 [inline]
kmem_cache_alloc_noprof+0x2bc/0x650 mm/slub.c:4873
alloc_filename fs/namei.c:142 [inline]
do_getname+0x2e/0x250 fs/namei.c:182
getname include/linux/fs.h:2512 [inline]
getname_maybe_null include/linux/fs.h:2519 [inline]
class_filename_maybe_null_constructor include/linux/fs.h:2543 [inline]
vfs_fstatat+0x45/0x170 fs/stat.c:368
__do_sys_newfstatat fs/stat.c:538 [inline]
__se_sys_newfstatat fs/stat.c:532 [inline]
__x64_sys_newfstatat+0x151/0x200 fs/stat.c:532
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Memory state around the buggy address:
ffff888109c42b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888109c42b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888109c42c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888109c42c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888109c42d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
***
KASAN: use-after-free Read in __ext4_check_dir_entry
tree: torvalds
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
base: 70b672833f4025341c11b22c7f83778a5cd611bc
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/7b860156-1ca9-441f-b899-ebfb5a09620d/config
syz repro: https://ci.syzbot.org/findings/21333690-a422-407b-92c7-9247a0075b74/syz_repro
loop1: lost filesystem error report for type 5 error -117
EXT4-fs (loop1): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
==================================================================
BUG: KASAN: use-after-free in ext4_dirent_get_data_len fs/ext4/ext4.h:4040 [inline]
BUG: KASAN: use-after-free in ext4_dir_entry_len fs/ext4/ext4.h:4060 [inline]
BUG: KASAN: use-after-free in __ext4_check_dir_entry+0x527/0xa70 fs/ext4/dir.c:96
Read of size 1 at addr ffff88810da3609c by task syz.1.20/5966
CPU: 0 UID: 0 PID: 5966 Comm: syz.1.20 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xba/0x230 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
ext4_dirent_get_data_len fs/ext4/ext4.h:4040 [inline]
ext4_dir_entry_len fs/ext4/ext4.h:4060 [inline]
__ext4_check_dir_entry+0x527/0xa70 fs/ext4/dir.c:96
ext4_inlinedir_to_tree+0x6be/0xbf0 fs/ext4/inline.c:1322
ext4_htree_fill_tree+0x50b/0x1230 fs/ext4/namei.c:1184
ext4_dx_readdir fs/ext4/dir.c:600 [inline]
ext4_readdir+0x2f7b/0x3870 fs/ext4/dir.c:146
iterate_dir+0x399/0x570 fs/readdir.c:108
__do_sys_getdents64 fs/readdir.c:412 [inline]
__se_sys_getdents64+0xf1/0x280 fs/readdir.c:397
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb82a19c819
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:00007fb82b01a028 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007fb82a415fa0 RCX: 00007fb82a19c819
RDX: 000000000000ff80 RSI: 9999999999999999 RDI: 0000000000000004
RBP: 00007fb82a232c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb82a416038 R14: 00007fb82a415fa0 R15: 00007ffdc30464e8
</TASK>
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88810da36000 pfn:0x10da36
flags: 0x17ff00000000000(node=0|zone=2|lastcpupid=0x7ff)
page_type: f0(buddy)
raw: 017ff00000000000 ffffea0004364708 ffffea000436a7c8 0000000000000000
raw: ffff88810da36000 0000000000000000 00000000f0000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2c00(GFP_NOIO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 15037633903, free_ts 26770192426
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
prep_new_page mm/page_alloc.c:1897 [inline]
get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
alloc_slab_page mm/slub.c:3292 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3481
new_slab mm/slub.c:3539 [inline]
refill_objects+0x331/0x3c0 mm/slub.c:7175
refill_sheaf mm/slub.c:2812 [inline]
__pcs_replace_empty_main+0x2e6/0x730 mm/slub.c:4615
alloc_from_pcs mm/slub.c:4717 [inline]
slab_alloc_node mm/slub.c:4851 [inline]
__do_kmalloc_node mm/slub.c:5259 [inline]
__kmalloc_noprof+0x474/0x760 mm/slub.c:5272
kmalloc_noprof include/linux/slab.h:954 [inline]
usb_alloc_urb+0x46/0x150 drivers/usb/core/urb.c:75
usb_internal_control_msg drivers/usb/core/message.c:110 [inline]
usb_control_msg+0x118/0x3e0 drivers/usb/core/message.c:167
usb_get_descriptor+0xb1/0x3e0 drivers/usb/core/message.c:852
usb_get_configuration+0x3b9/0x54f0 drivers/usb/core/config.c:986
usb_enumerate_device drivers/usb/core/hub.c:2527 [inline]
usb_new_device+0x145/0x16f0 drivers/usb/core/hub.c:2665
register_root_hub+0x270/0x5f0 drivers/usb/core/hcd.c:990
usb_add_hcd+0xba1/0x10b0 drivers/usb/core/hcd.c:2987
vhci_hcd_probe+0x1fa/0x3e0 drivers/usb/usbip/vhci_hcd.c:1401
platform_probe+0xf9/0x190 drivers/base/platform.c:1418
page last free pid 5262 tgid 5262 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1433 [inline]
__free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
__slab_free+0x263/0x2b0 mm/slub.c:5573
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4538 [inline]
slab_alloc_node mm/slub.c:4866 [inline]
kmem_cache_alloc_noprof+0x2bc/0x650 mm/slub.c:4873
alloc_empty_file+0x55/0x1d0 fs/file_table.c:237
path_openat+0x10f/0x3860 fs/namei.c:4816
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 fs/open.c:1366
do_sys_open fs/open.c:1372 [inline]
__do_sys_openat fs/open.c:1388 [inline]
__se_sys_openat fs/open.c:1383 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Memory state around the buggy address:
ffff88810da35f80: 00 00 00 00 00 00 00 04 fc fc fc fc fc fc fc fc
ffff88810da36000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88810da36080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88810da36100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88810da36180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
***
If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
Tested-by: syzbot@syzkaller.appspotmail.com
---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@googlegroups.com.
To test a patch for this bug, please reply with `#syz test`
(should be on a separate line).
The patch should be attached to the email.
Note: arguments like custom git repos and branches are not supported.
[-- Attachment #1.2: Type: text/html, Size: 53647 bytes --]
[-- Attachment #2: 0001-ext4-fix-syzbot.patch --]
[-- Type: application/octet-stream, Size: 4000 bytes --]
From 18df6683799e259479dc53260e59b5d1fdc6a143 Mon Sep 17 00:00:00 2001
From: Artem Blagodarenko <artem.blagodarenko@gmail.com>
Date: Sat, 18 Apr 2026 17:33:23 -0400
Subject: [PATCH] ext4: fix syzbot
Signed-off-by: Artem Blagodarenko <artem.blagodarenko@gmail.com>
---
fs/ext4/ext4.h | 33 ++++++++++++++++++++++++++++-----
fs/ext4/inline.c | 8 +++++++-
2 files changed, 35 insertions(+), 6 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 28271d42bfaf..c5d4aaed8e6e 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -4007,6 +4007,7 @@ static inline bool ext4_dir_entry_is_tail(struct ext4_dir_entry_2 *de)
/*
* ext4_dirent_get_data_len() - Compute the total dirdata length for an entry.
* @de: directory entry
+ * @rec_len: the record length of the directory entry (decoded)
*
* Computes the length of optional data stored after the filename (and its
* implicit NUL terminator). Each extension is indicated by a bit in the
@@ -4015,21 +4016,39 @@ static inline bool ext4_dir_entry_is_tail(struct ext4_dir_entry_2 *de)
*
* Returns 0 for tail entries and for entries with no dirdata.
*/
-static inline int ext4_dirent_get_data_len(struct ext4_dir_entry_2 *de)
+static inline int ext4_dirent_get_data_len(struct ext4_dir_entry_2 *de,
+ unsigned int rec_len)
{
__u8 extra_data_flags;
struct ext4_dirent_data_header *ddh;
int dlen = 0;
+ unsigned int offset;
if (ext4_dir_entry_is_tail(de))
return 0;
extra_data_flags = (de->file_type & ~EXT4_FT_MASK) >> 4;
- ddh = (struct ext4_dirent_data_header *)(de->name + de->name_len +
- 1 /* NUL terminator */);
+ /* offset from start of entry to after filename + NUL */
+ offset = EXT4_BASE_DIR_LEN + de->name_len + 1;
+
+ /* bounds check: ensure we start reading within the entry */
+ if (offset >= rec_len)
+ return 0;
+
+ ddh = (struct ext4_dirent_data_header *)((char *)de + offset);
while (extra_data_flags) {
if (extra_data_flags & 1) {
+ /* bounds check before reading ddh_length */
+ if (offset + sizeof(struct ext4_dirent_data_header) >
+ rec_len)
+ return dlen;
+
+ /* validate ddh_length is reasonable */
+ if (ddh->ddh_length == 0 || ddh->ddh_length >
+ rec_len - offset)
+ return dlen;
+
/*
* The first dirdata field is preceded by a NUL
* terminator byte that is already included in ddh's
@@ -4038,7 +4057,9 @@ static inline int ext4_dirent_get_data_len(struct ext4_dir_entry_2 *de)
if (dlen == 0)
dlen = 1; /* NUL terminator */
dlen += ddh->ddh_length;
- ddh = ext4_dirdata_next(ddh);
+ offset += ddh->ddh_length;
+ ddh = (struct ext4_dirent_data_header *)
+ ((char *)ddh + ddh->ddh_length);
}
extra_data_flags >>= 1;
}
@@ -4057,7 +4078,9 @@ static inline int ext4_dirent_get_data_len(struct ext4_dir_entry_2 *de)
static inline unsigned int ext4_dir_entry_len(struct ext4_dir_entry_2 *de,
const struct inode *dir)
{
- unsigned int dirdata = ext4_dirent_get_data_len(de);
+ unsigned int blocksize = (dir && dir->i_sb) ? dir->i_sb->s_blocksize : 4096;
+ unsigned int rec_len = ext4_rec_len_from_disk(de->rec_len, blocksize);
+ unsigned int dirdata = ext4_dirent_get_data_len(de, rec_len);
return ext4_dirent_rec_len(de->name_len + dirdata, dir);
}
diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index 071a637c8869..709acbf5e198 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -1318,7 +1318,13 @@ int ext4_inlinedir_to_tree(struct file *dir_file,
pos = EXT4_INLINE_DOTDOT_SIZE;
} else {
de = (struct ext4_dir_entry_2 *)(dir_buf + pos);
- pos += ext4_rec_len_from_disk(de->rec_len, inline_size);
+ /* Use ext4_dir_entry_len to account for dirdata extensions */
+ pos += ext4_dir_entry_len(de, dir);
+ /* Validate pos doesn't exceed buffer to prevent use-after-free */
+ if (pos > inline_size) {
+ ret = count;
+ goto out;
+ }
if (ext4_check_dir_entry(inode, dir_file, de,
iloc.bh, dir_buf,
inline_size, pos)) {
--
2.43.7
^ permalink raw reply related [flat|nested] 3+ messages in thread