[Android 5.10] KASAN: use-after-free Read in ext4_convert_inline_data_nolock (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6321e6c974f1 Merge 60e3f4ff02d1 ("Bluetooth: fix locking i..
git tree: android13-5.10-lts
console output: https://syzkaller.appspot.com/x/log.txt?x=1417ccfe580000
kernel config: https://syzkaller.appspot.com/x/.config?x=29727da16e7886e6
dashboard link: https://syzkaller.appspot.com/bug?extid=90de828ca945fb262dc0
compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16eb5b7a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16e822ae580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/acb40e73bff0/disk-6321e6c9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/20d98296ad56/vmlinux-6321e6c9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d92b8a3ae122/bzImage-6321e6c9.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/185800220da3/mount_0.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=16bf4d56580000)
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/4e81e0b92807/mount_8.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=11c2501c580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+90de82...@syzkaller.appspotmail.com

EXT4-fs: Warning: mounting with data=journal disables delayed allocation, dioread_nolock, O_DIRECT and fast_commit support!
EXT4-fs (loop2): encrypted files will use data=ordered instead of data journaling mode
EXT4-fs (loop2): 1 truncate cleaned up
EXT4-fs (loop2): mounted filesystem without journal. Opts: noblock_validity,max_batch_time=0x0000000000000002,lazytime,block_validity,stripe=0x000000000000000d,nombcache,,errors=continue
==================================================================
BUG: KASAN: slab-out-of-bounds in ext4_read_inline_data fs/ext4/inline.c:209 [inline]
BUG: KASAN: slab-out-of-bounds in ext4_convert_inline_data_nolock+0x313/0xcc0 fs/ext4/inline.c:1242
Read of size 68 at addr ffff888110f9bc80 by task syz.2.17/394

CPU: 1 PID: 394 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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+0x100/0x140 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_convert_inline_data_nolock+0x313/0xcc0 fs/ext4/inline.c:1242
ext4_try_add_inline_entry+0x73d/0xa70 fs/ext4/inline.c:1367
ext4_add_entry+0x674/0xf90 fs/ext4/namei.c:2414
ext4_mkdir+0x509/0xc60 fs/ext4/namei.c:3019
vfs_mkdir+0x42c/0x600 fs/namei.c:3798
do_mkdirat+0x14c/0x340 fs/namei.c:3820
__do_sys_mkdirat fs/namei.c:3831 [inline]
__se_sys_mkdirat fs/namei.c:3829 [inline]
__x64_sys_mkdirat+0x7b/0x90 fs/namei.c:3829
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f4982849cc7
Code: 00 66 90 48 89 f2 b9 00 01 00 00 48 89 fe bf 9c ff ff ff e9 db f7 ff ff 66 2e 0f 1f 84 00 00 00 00 00 90 b8 02 01 00 00 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:00007ffe47e266d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007ffe47e26760 RCX: 00007f4982849cc7
RDX: 00000000000001ff RSI: 0000200000000080 RDI: 00000000ffffff9c
RBP: 0000200000000140 R08: 0000200000000080 R09: 0000000000000000
R10: 0000200000000140 R11: 0000000000000246 R12: 0000200000000080
R13: 00007ffe47e26720 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 95:
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_kmalloc mm/kasan/common.c:509 [inline]
__kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518
kasan_kmalloc include/linux/kasan.h:254 [inline]
kmem_cache_alloc_trace+0x179/0x2e0 mm/slub.c:2979
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:667 [inline]
kernfs_iop_get_link+0x66/0x600 fs/kernfs/symlink.c:136
vfs_readlink+0x16f/0x3e0 fs/namei.c:4728
do_readlinkat+0x251/0x490 fs/stat.c:426
__do_sys_readlink fs/stat.c:447 [inline]
__se_sys_readlink fs/stat.c:444 [inline]
__x64_sys_readlink+0x7f/0x90 fs/stat.c:444
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 95:
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]
kfree+0xc0/0x270 mm/slub.c:4196
kfree_link+0x15/0x20 fs/libfs.c:1220
do_delayed_call include/linux/delayed_call.h:28 [inline]
vfs_readlink+0x220/0x3e0 fs/namei.c:4733
do_readlinkat+0x251/0x490 fs/stat.c:426
__do_sys_readlink fs/stat.c:447 [inline]
__se_sys_readlink fs/stat.c:444 [inline]
__x64_sys_readlink+0x7f/0x90 fs/stat.c:444
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 ffff888110f9a000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 3200 bytes to the right of
4096-byte region [ffff888110f9a000, ffff888110f9b000)
The buggy address belongs to the page:
page:ffffea000443e600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x110f98
head:ffffea000443e600 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100042c00
raw: 0000000000000000 0000000000040004 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 107, ts 5385175749, 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+0x176/0x190 mm/page_alloc.c:2462
get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
__alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
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+0x2f8/0x4c0 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_trace+0x1a8/0x2e0 mm/slub.c:2977
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:667 [inline]
kernfs_iop_get_link+0x66/0x600 fs/kernfs/symlink.c:136
vfs_readlink+0x16f/0x3e0 fs/namei.c:4728
do_readlinkat+0x251/0x490 fs/stat.c:426
__do_sys_readlink fs/stat.c:447 [inline]
__se_sys_readlink fs/stat.c:444 [inline]
__x64_sys_readlink+0x7f/0x90 fs/stat.c:444
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:
ffff888110f9bb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888110f9bc00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888110f9bc80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff888110f9bd00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888110f9bd80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
EXT4-fs error (device loop2): ext4_check_all_de:659: inode #12: block 7: comm syz.2.17: bad entry in directory: directory entry overrun - offset=0, inode=901261600, rec_len=7976, size=124 fake=0


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