[v6.6] KASAN: slab-out-of-bounds Read in dtReadFirst

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5fa4793a2d2d Linux 6.6.119
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1314e022580000
kernel config: https://syzkaller.appspot.com/x/.config?x=691a6769a86ac817
dashboard link: https://syzkaller.appspot.com/bug?extid=1bf0cad7a945867a458d
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=122f109a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=102f2f1a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/63699875f1dd/disk-5fa4793a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8506652fcb6f/vmlinux-5fa4793a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1b30ceed1710/bzImage-5fa4793a.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/e2da918333d5/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=148cab92580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1bf0ca...@syzkaller.appspotmail.com

syz.0.17[5930]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set
loop0: detected capacity change from 0 to 32768
==================================================================
BUG: KASAN: slab-out-of-bounds in addressPXD fs/jfs/jfs_types.h:80 [inline]
BUG: KASAN: slab-out-of-bounds in dtReadFirst+0x502/0x920 fs/jfs/jfs_dtree.c:3108
Read of size 4 at addr ffff88805f931210 by task syz.0.17/5930

CPU: 1 PID: 5930 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xac/0x220 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
addressPXD fs/jfs/jfs_types.h:80 [inline]
dtReadFirst+0x502/0x920 fs/jfs/jfs_dtree.c:3108
jfs_readdir+0x6f6/0x3a90 fs/jfs/jfs_dtree.c:2821
wrap_directory_iterator+0x92/0xd0 fs/readdir.c:67
iterate_dir+0x1c2/0x580 fs/readdir.c:106
__do_sys_getdents64 fs/readdir.c:405 [inline]
__se_sys_getdents64+0xe9/0x260 fs/readdir.c:390
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f167938f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe3016dff8 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007f16795e5fa0 RCX: 00007f167938f749
RDX: 0000000000000099 RSI: 0000200000000400 RDI: 0000000000000005
RBP: 00007f1679413f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f16795e5fa0 R14: 00007f16795e5fa0 R15: 0000000000000003
</TASK>

Allocated by task 5930:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
slab_alloc_node mm/slub.c:3495 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc_lru+0x115/0x2e0 mm/slub.c:3526
alloc_inode_sb include/linux/fs.h:2946 [inline]
jfs_alloc_inode+0x28/0x60 fs/jfs/super.c:105
alloc_inode fs/inode.c:261 [inline]
new_inode_pseudo+0x63/0x1d0 fs/inode.c:1049
new_inode+0x22/0x1b0 fs/inode.c:1075
ialloc+0x4c/0x950 fs/jfs/jfs_inode.c:48
jfs_create+0x18b/0xa40 fs/jfs/namei.c:92
lookup_open fs/namei.c:3496 [inline]
open_last_lookups fs/namei.c:3564 [inline]
path_openat+0x1277/0x3190 fs/namei.c:3794
do_filp_open+0x1c5/0x3d0 fs/namei.c:3824
do_sys_openat2+0x12c/0x1c0 fs/open.c:1421
do_sys_open fs/open.c:1436 [inline]
__do_sys_openat fs/open.c:1452 [inline]
__se_sys_openat fs/open.c:1447 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1447
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88805f930940
which belongs to the cache jfs_ip of size 2240
The buggy address is located 16 bytes to the right of
allocated 2240-byte region [ffff88805f930940, ffff88805f931200)

The buggy address belongs to the physical page:
page:ffffea00017e4c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5f930
head:ffffea00017e4c00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88807c0ebc01
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888018b853c0 dead000000000122 0000000000000000
raw: 0000000000000000 00000000800d000d 00000001ffffffff ffff88807c0ebc01
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Reclaimable, gfp_mask 0x1d2050(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 5930, tgid 5930 (syz.0.17), ts 105322123817, free_ts 28628187766
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
prep_new_page mm/page_alloc.c:1561 [inline]
get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
__alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
alloc_slab_page+0x5d/0x170 mm/slub.c:1881
allocate_slab mm/slub.c:2028 [inline]
new_slab+0x87/0x2e0 mm/slub.c:2081
___slab_alloc+0xc6d/0x1300 mm/slub.c:3253
__slab_alloc mm/slub.c:3339 [inline]
__slab_alloc_node mm/slub.c:3392 [inline]
slab_alloc_node mm/slub.c:3485 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc_lru+0x1ae/0x2e0 mm/slub.c:3526
alloc_inode_sb include/linux/fs.h:2946 [inline]
jfs_alloc_inode+0x28/0x60 fs/jfs/super.c:105
alloc_inode fs/inode.c:261 [inline]
iget_locked+0x1ad/0x840 fs/inode.c:1359
jfs_iget+0x24/0x440 fs/jfs/inode.c:29
jfs_fill_super+0x70c/0xac0 fs/jfs/super.c:580
mount_bdev+0x22b/0x2d0 fs/super.c:1643
legacy_get_tree+0xea/0x180 fs/fs_context.c:662
vfs_get_tree+0x8c/0x280 fs/super.c:1764
do_new_mount+0x24b/0xa40 fs/namespace.c:3386
do_mount fs/namespace.c:3726 [inline]
__do_sys_mount fs/namespace.c:3935 [inline]
__se_sys_mount+0x2da/0x3c0 fs/namespace.c:3912
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1154 [inline]
free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
free_contig_range+0xa1/0x160 mm/page_alloc.c:6369
destroy_args+0x80/0x850 mm/debug_vm_pgtable.c:1015
debug_vm_pgtable+0x3cc/0x410 mm/debug_vm_pgtable.c:1400
do_one_initcall+0x1fd/0x750 init/main.c:1250
do_initcall_level+0x137/0x1f0 init/main.c:1312
do_initcalls+0x69/0xd0 init/main.c:1328
kernel_init_freeable+0x3d2/0x570 init/main.c:1565
kernel_init+0x1d/0x1c0 init/main.c:1455
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Memory state around the buggy address:
ffff88805f931100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88805f931180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88805f931200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff88805f931280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88805f931300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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