[Android 5.15] KASAN: use-after-free Read in ext4_inlinedir_to_tree

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 00b50d06692d Merge 8368be8a5072 ("coresight: etm4x: Add co..
git tree: android13-5.15-lts
console output: https://syzkaller.appspot.com/x/log.txt?x=17ccc05a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=deffac0a782f1cb0
dashboard link: https://syzkaller.appspot.com/bug?extid=6ff629dda3dd0ffdf059
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1670d13a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=102cc05a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e15cc4396286/disk-00b50d06.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bc02335d0e47/vmlinux-00b50d06.xz
kernel image: https://storage.googleapis.com/syzbot-assets/85f3421c6737/bzImage-00b50d06.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/4c2b3d2a68f8/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=13362bfa580000)
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/97e7c90e6dbc/mount_7.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=130af52a580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6ff629...@syzkaller.appspotmail.com

EXT4-fs (loop2): mounted filesystem without journal. Opts: errors=remount-ro,. Quota mode: none.
EXT4-fs error (device loop2): ext4_validate_block_bitmap:438: comm syz.2.17: bg 0: block 465: padding at end of block bitmap is not set
EXT4-fs (loop2): Remounting filesystem read-only
==================================================================
BUG: KASAN: slab-out-of-bounds in ext4_read_inline_data fs/ext4/inline.c:210 [inline]
BUG: KASAN: slab-out-of-bounds in ext4_inlinedir_to_tree+0x508/0xfe0 fs/ext4/inline.c:1433
Read of size 52 at addr ffff88811d55fb97 by task syz.2.17/372

CPU: 1 PID: 372 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
__dump_stack+0x21/0x30 lib/dump_stack.c:88
dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:427 [inline]
kasan_report+0xf1/0x140 mm/kasan/report.c:444
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:210 [inline]
ext4_inlinedir_to_tree+0x508/0xfe0 fs/ext4/inline.c:1433
ext4_htree_fill_tree+0x508/0x1160 fs/ext4/namei.c:1211
ext4_dx_readdir fs/ext4/dir.c:609 [inline]
ext4_readdir+0x2cdb/0x3b20 fs/ext4/dir.c:145
iterate_dir+0x260/0x600 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
x64_sys_call+0xb4/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:79
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f638b57ecb9
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:00007ffc9022aaf8 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007f638b7f9fa0 RCX: 00007f638b57ecb9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007f638b5ecbf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f638b7f9fac R14: 00007f638b7f9fa0 R15: 00007f638b7f9fa0
</TASK>

Allocated by task 287:
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:433 [inline]
____kasan_kmalloc mm/kasan/common.c:512 [inline]
__kasan_kmalloc+0xda/0x110 mm/kasan/common.c:521
kasan_kmalloc include/linux/kasan.h:227 [inline]
kmem_cache_alloc_trace+0x119/0x270 mm/slub.c:3274
kmalloc include/linux/slab.h:619 [inline]
kzalloc include/linux/slab.h:750 [inline]
cgroup1_root_to_use kernel/cgroup/cgroup-v1.c:1219 [inline]
cgroup1_get_tree+0x785/0xc70 kernel/cgroup/cgroup-v1.c:1243
vfs_get_tree+0x89/0x260 fs/super.c:1530
do_new_mount+0x25a/0xa20 fs/namespace.c:3034
path_mount+0x659/0xff0 fs/namespace.c:3364
do_mount fs/namespace.c:3377 [inline]
__do_sys_mount fs/namespace.c:3585 [inline]
__se_sys_mount+0x320/0x390 fs/namespace.c:3562
__x64_sys_mount+0xbf/0xd0 fs/namespace.c:3562
x64_sys_call+0x6bf/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:166
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 42:
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:365
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
kasan_slab_free include/linux/kasan.h:193 [inline]
slab_free_hook mm/slub.c:1728 [inline]
slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
slab_free mm/slub.c:3526 [inline]
kfree+0xc4/0x270 mm/slub.c:4588
css_free_rwork_fn+0x862/0xc60 kernel/cgroup/cgroup.c:-1
process_one_work+0x6be/0xba0 kernel/workqueue.c:2325
worker_thread+0xa59/0x1200 kernel/workqueue.c:2472
kthread+0x411/0x500 kernel/kthread.c:337
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

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
insert_work+0x51/0x310 kernel/workqueue.c:1373
__queue_work+0x8e5/0xc60 kernel/workqueue.c:1539
rcu_work_rcufn+0x47/0x50 kernel/workqueue.c:1775
rcu_do_batch+0x532/0xbe0 kernel/rcu/tree.c:2523
rcu_core+0x5ee/0xf80 kernel/rcu/tree.c:2763
rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776
handle_softirqs+0x250/0x560 kernel/softirq.c:583
__do_softirq kernel/softirq.c:621 [inline]
invoke_softirq kernel/softirq.c:443 [inline]
__irq_exit_rcu+0x52/0xf0 kernel/softirq.c:670
irq_exit_rcu+0x9/0x10 kernel/softirq.c:682
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0xa9/0xc0 arch/x86/kernel/apic/apic.c:1108
asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:676

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_noalloc+0xb/0x10 mm/kasan/generic.c:358
__call_rcu_common kernel/rcu/tree.c:3011 [inline]
call_rcu+0x10b/0xf80 kernel/rcu/tree.c:3129
queue_rcu_work+0x86/0xa0 kernel/workqueue.c:1795
css_release_work_fn+0x46e/0x5f0 kernel/cgroup/cgroup.c:5339
process_one_work+0x6be/0xba0 kernel/workqueue.c:2325
worker_thread+0xa59/0x1200 kernel/workqueue.c:2472
kthread+0x411/0x500 kernel/kthread.c:337
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

The buggy address belongs to the object at ffff88811d55c000
which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 7063 bytes to the right of
8192-byte region [ffff88811d55c000, ffff88811d55e000)
The buggy address belongs to the page:
page:ffffea0004755600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11d558
head:ffffea0004755600 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 dead000000000122 ffff888100043500
raw: 0000000000000000 0000000000020002 00000001ffffffff 0000000000000000
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 287, ts 23779439743, free_ts 13754259789
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2605
prep_new_page+0x1c/0x110 mm/page_alloc.c:2611
get_page_from_freelist+0x2d3a/0x2dc0 mm/page_alloc.c:4485
__alloc_pages+0x1a2/0x460 mm/page_alloc.c:5808
alloc_slab_page mm/slub.c:-1 [inline]
allocate_slab mm/slub.c:1937 [inline]
new_slab+0xa1/0x4d0 mm/slub.c:2000
___slab_alloc+0x381/0x810 mm/slub.c:3033
__slab_alloc+0x49/0x90 mm/slub.c:3120
slab_alloc_node mm/slub.c:3211 [inline]
slab_alloc mm/slub.c:3255 [inline]
kmem_cache_alloc_trace+0x146/0x270 mm/slub.c:3272
kmalloc include/linux/slab.h:619 [inline]
kzalloc include/linux/slab.h:750 [inline]
cgroup1_root_to_use kernel/cgroup/cgroup-v1.c:1219 [inline]
cgroup1_get_tree+0x785/0xc70 kernel/cgroup/cgroup-v1.c:1243
vfs_get_tree+0x89/0x260 fs/super.c:1530
do_new_mount+0x25a/0xa20 fs/namespace.c:3034
path_mount+0x659/0xff0 fs/namespace.c:3364
do_mount fs/namespace.c:3377 [inline]
__do_sys_mount fs/namespace.c:3585 [inline]
__se_sys_mount+0x320/0x390 fs/namespace.c:3562
__x64_sys_mount+0xbf/0xd0 fs/namespace.c:3562
x64_sys_call+0x6bf/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:166
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1472 [inline]
free_pcp_prepare mm/page_alloc.c:1544 [inline]
free_unref_page_prepare+0x542/0x550 mm/page_alloc.c:3534
free_unref_page+0xae/0x540 mm/page_alloc.c:3616
__put_single_page mm/swap.c:98 [inline]
__put_page+0xad/0xe0 mm/swap.c:129
put_page include/linux/mm.h:1306 [inline]
anon_pipe_buf_release+0x183/0x200 fs/pipe.c:137
pipe_buf_release include/linux/pipe_fs_i.h:219 [inline]
pipe_read+0x53b/0x1010 fs/pipe.c:323
call_read_iter include/linux/fs.h:2206 [inline]
new_sync_read fs/read_write.c:404 [inline]
vfs_read+0x6c9/0xc40 fs/read_write.c:485
ksys_read+0x149/0x250 fs/read_write.c:623
__do_sys_read fs/read_write.c:633 [inline]
__se_sys_read fs/read_write.c:631 [inline]
__x64_sys_read+0x7b/0x90 fs/read_write.c:631
x64_sys_call+0x96d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
ffff88811d55fa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88811d55fb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88811d55fb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff88811d55fc00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88811d55fc80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
EXT4-fs error (device loop2): ext4_inlinedir_to_tree:1471: inode #12: block 7: comm syz.2.17: path /0/file1/file0: bad entry in directory: rec_len % 4 != 0 - offset=35110, inode=3517778242, rec_len=35106, size=112 fake=0
EXT4-fs (loop2): Remounting filesystem read-only


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