KASAN: slab-out-of-bounds Read in dtReadFirst

Status: upstream: reported C repro on 2025/12/25 14:42
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+1bf0cad7a945867a458d@syzkaller.appspotmail.com
First crash: 214d, last: 51d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (3)
Date Name Commit Repro Result
2026/05/27 linux-6.6.y (ToT) 0a40c6fbd105 C [report] KASAN: slab-out-of-bounds Read in dtReadFirst
2025/12/26 upstream (ToT) ccd1cdca5cd4 C [report] KASAN: slab-out-of-bounds Read in dtReadFirst
2026/05/27 upstream (ToT) eb3f4b7426cf C Didn't crash
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 UBSAN: array-index-out-of-bounds in dtReadFirst origin:lts-only 19 C error 25 148d 610d 0/3 upstream: reported C repro on 2024/11/25 10:09
upstream UBSAN: array-index-out-of-bounds in dtReadFirst jfs 19 C error 200 590d 818d 28/29 fixed on 2024/12/16 09:50
linux-5.15 UBSAN: array-index-out-of-bounds in dtReadFirst origin:upstream 17 C error 36 8d12h 820d 0/3 upstream: reported C repro on 2024/04/28 12:32
upstream UBSAN: array-index-out-of-bounds in dtReadFirst (2) jfs 19 C error 119 455d 584d 28/29 fixed on 2025/06/10 16:19
upstream KASAN: slab-out-of-bounds Read in dtReadFirst prio:high jfs 19 C error error 69 106d 383d 0/29 upstream: reported C repro on 2025/07/09 11:02
▶ ▼ Fix bisection attempts (2)
Created Duration User Patch Repo Result
2026/06/01 05:29 13m fix candidate upstream error job log
2026/01/24 14:46 0m bisect fix linux-6.6.y error job log

Sample crash report:
syz.0.17[5933]: 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 ffff888072bf4050 by task syz.0.17/5933

CPU: 0 PID: 5933 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 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+0x74f/0x3bb0 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+0xf6/0x270 fs/readdir.c:390
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0def19ce59
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:00007ffe4f603898 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007f0def415fa0 RCX: 00007f0def19ce59
RDX: 00000000000000a2 RSI: 00002000000002c0 RDI: 0000000000000005
RBP: 00007f0def232d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0def415fac R14: 00007f0def415fa0 R15: 00007f0def415fa0
 </TASK>

Allocated by task 5933:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4b0 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+0x111/0x2d0 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+0x1d6/0xac0 fs/jfs/namei.c:92
 lookup_open fs/namei.c:3496 [inline]
 open_last_lookups fs/namei.c:3564 [inline]
 path_openat+0x12a0/0x3230 fs/namei.c:3794
 do_filp_open+0x1f5/0x430 fs/namei.c:3824
 do_sys_openat2+0x134/0x1d0 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:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888072bf3780
 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 [ffff888072bf3780, ffff888072bf4040)

The buggy address belongs to the physical page:
page:ffffea0001cafc00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x72bf0
head:ffffea0001cafc00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff8880742d0b01
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888018f6cdc0 dead000000000122 0000000000000000
raw: 0000000000000000 00000000800d000d 00000001ffffffff ffff8880742d0b01
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 5933, tgid 5933 (syz.0.17), ts 88494917961, free_ts 24732885590
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1581
 prep_new_page mm/page_alloc.c:1588 [inline]
 get_page_from_freelist+0x1951/0x19e0 mm/page_alloc.c:3220
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4500
 alloc_slab_page+0x5d/0x160 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5d/0x12f0 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+0x1aa/0x2d0 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
 jfs_fill_super+0x39c/0xad0 fs/jfs/super.c:544
 mount_bdev+0x221/0x2d0 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+0x2e7/0x3d0 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:1181 [inline]
 free_unref_page_prepare+0x7b2/0x8c0 mm/page_alloc.c:2365
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2458
 free_contig_range+0xa1/0x150 mm/page_alloc.c:6420
 destroy_args+0x80/0x850 mm/debug_vm_pgtable.c:1015
 debug_vm_pgtable+0x411/0x440 mm/debug_vm_pgtable.c:1400
 do_one_initcall+0x242/0x790 init/main.c:1249
 do_initcall_level+0x137/0x1f0 init/main.c:1311
 do_initcalls+0x69/0xd0 init/main.c:1327
 kernel_init_freeable+0x3ed/0x580 init/main.c:1564
 kernel_init+0x1d/0x1c0 init/main.c:1454
 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:
 ffff888072bf3f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888072bf3f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888072bf4000: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
                                                 ^
 ffff888072bf4080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888072bf4100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/06 20:10 linux-6.6.y 924b4a879cbb cc095639 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in dtReadFirst
2025/12/25 14:41 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in dtReadFirst
* Struck through repros no longer work on HEAD.