Message-ID: <691c8417.a70a0220.3124cb.00ca.GAE@google.com>
Date: Tue, 18 Nov 2025 06:35:03 -0800
From: syzbot <syzbot+5f7f0caf9979e9d09ff8@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, 
	yun.zhou@...driver.com
Subject: Re: [syzbot] [jfs?] UBSAN: array-index-out-of-bounds in dtInsertEntry

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-out-of-bounds Read in dtSplitPage

read_mapping_page failed!
ERROR: (device loop0): txCommit: 
read_mapping_page failed!
ERROR: (device loop0): txCommit: 
==================================================================
BUG: KASAN: slab-out-of-bounds in dtSplitPage+0x121b/0x38c0 fs/jfs/jfs_dtree.c:-1
Read of size 1 at addr ffff888060f891dd by task syz.0.16/6471

CPU: 0 UID: 0 PID: 6471 Comm: syz.0.16 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 dtSplitPage+0x121b/0x38c0 fs/jfs/jfs_dtree.c:-1
 dtSplitUp fs/jfs/jfs_dtree.c:1092 [inline]
 dtInsert+0x100c/0x5d10 fs/jfs/jfs_dtree.c:871
 jfs_mkdir+0x6ec/0xa70 fs/jfs/namei.c:270
 vfs_mkdir+0x306/0x510 fs/namei.c:4453
 do_mkdirat+0x247/0x590 fs/namei.c:4486
 __do_sys_mkdirat fs/namei.c:4503 [inline]
 __se_sys_mkdirat fs/namei.c:4501 [inline]
 __x64_sys_mkdirat+0x87/0xa0 fs/namei.c:4501
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8cecf8d1d7
Code: 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 02 01 00 00 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:00007f8cede76e68 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007f8cede76ef0 RCX: 00007f8cecf8d1d7
RDX: 00000000000001ff RSI: 0000200000000040 RDI: 00000000ffffff9c
RBP: 0000200000000140 R08: 00002000000000c0 R09: 0000000000000000
R10: 0000200000000140 R11: 0000000000000246 R12: 0000200000000040
R13: 00007f8cede76eb0 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Allocated by task 6471:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 unpoison_slab_object mm/kasan/common.c:342 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:368
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4978 [inline]
 slab_alloc_node mm/slub.c:5288 [inline]
 kmem_cache_alloc_lru_noprof+0x35d/0x6d0 mm/slub.c:5307
 jfs_alloc_inode+0x28/0x70 fs/jfs/super.c:105
 alloc_inode+0x6a/0x1b0 fs/inode.c:346
 iget_locked+0x106/0x580 fs/inode.c:1445
 jfs_iget+0x24/0x470 fs/jfs/inode.c:29
 jfs_lookup+0x1c5/0x380 fs/jfs/namei.c:1469
 __lookup_slow+0x297/0x3d0 fs/namei.c:1816
 lookup_slow+0x53/0x70 fs/namei.c:1833
 walk_component+0x2d2/0x400 fs/namei.c:2151
 lookup_last fs/namei.c:2652 [inline]
 path_lookupat+0x163/0x430 fs/namei.c:2676
 filename_lookup+0x212/0x570 fs/namei.c:2705
 user_path_at+0x3a/0x60 fs/namei.c:3215
 __do_sys_chdir fs/open.c:561 [inline]
 __se_sys_chdir+0x91/0x280 fs/open.c:555
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888060f88928
 which belongs to the cache jfs_ip of size 2216
The buggy address is located 13 bytes to the right of
 allocated 2216-byte region [ffff888060f88928, ffff888060f891d0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x60f88
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888077ec2e01
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801e397280 dead000000000122 0000000000000000
raw: 0000000000000000 00000000800d000d 00000000f5000000 ffff888077ec2e01
head: 00fff00000000040 ffff88801e397280 dead000000000122 0000000000000000
head: 0000000000000000 00000000800d000d 00000000f5000000 ffff888077ec2e01
head: 00fff00000000003 ffffea000183e201 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 Reclaimable, gfp_mask 0xd2050(__GFP_RECLAIMABLE|__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6471, tgid 6470 (syz.0.16), ts 129317552975, free_ts 22248192864
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1850
 prep_new_page mm/page_alloc.c:1858 [inline]
 get_page_from_freelist+0x2356/0x2430 mm/page_alloc.c:3884
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5183
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:3059 [inline]
 allocate_slab+0x96/0x350 mm/slub.c:3232
 new_slab mm/slub.c:3286 [inline]
 ___slab_alloc+0xf56/0x1990 mm/slub.c:4655
 __slab_alloc+0x65/0x100 mm/slub.c:4778
 __slab_alloc_node mm/slub.c:4854 [inline]
 slab_alloc_node mm/slub.c:5276 [inline]
 kmem_cache_alloc_lru_noprof+0x3ef/0x6d0 mm/slub.c:5307
 jfs_alloc_inode+0x28/0x70 fs/jfs/super.c:105
 alloc_inode+0x6a/0x1b0 fs/inode.c:346
 iget_locked+0x106/0x580 fs/inode.c:1445
 jfs_iget+0x24/0x470 fs/jfs/inode.c:29
 jfs_fill_super+0x8ad/0xd80 fs/jfs/super.c:547
 get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1698
 vfs_get_tree+0x92/0x2b0 fs/super.c:1758
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3642 [inline]
 do_new_mount+0x302/0xa10 fs/namespace.c:3718
page last free pid 1 tgid 1 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1394 [inline]
 __free_frozen_pages+0xbb1/0xd20 mm/page_alloc.c:2906
 __free_pages mm/page_alloc.c:5302 [inline]
 free_contig_range+0x1bd/0x4a0 mm/page_alloc.c:7146
 destroy_args+0x69/0x660 mm/debug_vm_pgtable.c:958
 debug_vm_pgtable+0x39f/0x3b0 mm/debug_vm_pgtable.c:1345
 do_one_initcall+0x236/0x820 init/main.c:1283
 do_initcall_level+0x104/0x190 init/main.c:1345
 do_initcalls+0x59/0xa0 init/main.c:1361
 kernel_init_freeable+0x334/0x4b0 init/main.c:1593
 kernel_init+0x1d/0x1d0 init/main.c:1483
 ret_from_fork+0x4bc/0x870 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:
 ffff888060f89080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888060f89100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888060f89180: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
                                                    ^
 ffff888060f89200: fc fc fc fc fc fc fc fc fc fc 00 00 00 00 00 00
 ffff888060f89280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


Tested on:

commit:         e7c375b1 Merge tag 'vfs-6.18-rc7.fixes' of gitolite.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10ca3914580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=38deb25bbc2fa41e
dashboard link: https://syzkaller.appspot.com/bug?extid=5f7f0caf9979e9d09ff8
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=110df212580000

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