Message-ID: <691d3672.a70a0220.2ea503.000a.GAE@google.com>
Date: Tue, 18 Nov 2025 19:16:02 -0800
From: syzbot <syzbot+4c1966e88c28fa96e053@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, 
	yun.zhou@...driver.com
Subject: Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in dbSplit (3)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in release_metapage

loop0: detected capacity change from 0 to 32768
==================================================================
BUG: KASAN: slab-use-after-free in drop_metapage fs/jfs/jfs_metapage.c:312 [inline]
BUG: KASAN: slab-use-after-free in release_metapage+0x738/0xaa0 fs/jfs/jfs_metapage.c:893
Read of size 8 at addr ffff88801fef6120 by task syz.0.591/7013

CPU: 0 UID: 0 PID: 7013 Comm: syz.0.591 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
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
 drop_metapage fs/jfs/jfs_metapage.c:312 [inline]
 release_metapage+0x738/0xaa0 fs/jfs/jfs_metapage.c:893
 write_metapage fs/jfs/jfs_metapage.h:75 [inline]
 flush_metapage fs/jfs/jfs_metapage.h:81 [inline]
 ea_write+0x658/0xdd0 fs/jfs/xattr.c:280
 ea_put fs/jfs/xattr.c:619 [inline]
 __jfs_setxattr+0xa01/0x1120 fs/jfs/xattr.c:792
 __jfs_xattr_set+0xda/0x170 fs/jfs/xattr.c:941
 __vfs_setxattr+0x43c/0x480 fs/xattr.c:200
 __vfs_setxattr_noperm+0x12d/0x660 fs/xattr.c:234
 vfs_setxattr+0x16b/0x2f0 fs/xattr.c:321
 do_setxattr fs/xattr.c:636 [inline]
 filename_setxattr+0x274/0x600 fs/xattr.c:665
 path_setxattrat+0x364/0x3a0 fs/xattr.c:713
 __do_sys_lsetxattr fs/xattr.c:754 [inline]
 __se_sys_lsetxattr fs/xattr.c:750 [inline]
 __x64_sys_lsetxattr+0xbf/0xe0 fs/xattr.c:750
 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: 0033:0x7f7c5938e969
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:00007f7c5a2af038 EFLAGS: 00000246 ORIG_RAX: 00000000000000bd
RAX: ffffffffffffffda RBX: 00007f7c595b5fa0 RCX: 00007f7c5938e969
RDX: 0000200000000040 RSI: 00002000000000c0 RDI: 0000200000000100
RBP: 00007f7c59410ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000fe37 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f7c595b5fa0 R15: 00007ffeee4d4ad8
 </TASK>

Allocated by task 7013:
 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_noprof+0x367/0x6e0 mm/slub.c:5295
 mempool_alloc_noprof+0x1a7/0x510 mm/mempool.c:406
 alloc_metapage fs/jfs/jfs_metapage.c:264 [inline]
 __get_metapage+0x509/0xe20 fs/jfs/jfs_metapage.c:761
 ea_write+0x5e6/0xdd0 fs/jfs/xattr.c:256
 ea_put fs/jfs/xattr.c:619 [inline]
 __jfs_setxattr+0xa01/0x1120 fs/jfs/xattr.c:792
 __jfs_xattr_set+0xda/0x170 fs/jfs/xattr.c:941
 __vfs_setxattr+0x43c/0x480 fs/xattr.c:200
 __vfs_setxattr_noperm+0x12d/0x660 fs/xattr.c:234
 vfs_setxattr+0x16b/0x2f0 fs/xattr.c:321
 do_setxattr fs/xattr.c:636 [inline]
 filename_setxattr+0x274/0x600 fs/xattr.c:665
 path_setxattrat+0x364/0x3a0 fs/xattr.c:713
 __do_sys_lsetxattr fs/xattr.c:754 [inline]
 __se_sys_lsetxattr fs/xattr.c:750 [inline]
 __x64_sys_lsetxattr+0xbf/0xe0 fs/xattr.c:750
 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

Freed by task 73:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 __kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:587
 kasan_save_free_info mm/kasan/kasan.h:406 [inline]
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2543 [inline]
 slab_free mm/slub.c:6642 [inline]
 kmem_cache_free+0x19b/0x690 mm/slub.c:6752
 free_metapage fs/jfs/jfs_metapage.c:280 [inline]
 metapage_release_folio+0x46c/0x5b0 fs/jfs/jfs_metapage.c:637
 shrink_folio_list+0x20ac/0x4c70 mm/vmscan.c:1519
 evict_folios+0x471e/0x57c0 mm/vmscan.c:4745
 try_to_shrink_lruvec+0x8a3/0xb50 mm/vmscan.c:4908
 shrink_one+0x21b/0x7c0 mm/vmscan.c:4953
 shrink_many mm/vmscan.c:5016 [inline]
 lru_gen_shrink_node mm/vmscan.c:5094 [inline]
 shrink_node+0x315d/0x3780 mm/vmscan.c:6081
 kswapd_shrink_node mm/vmscan.c:6941 [inline]
 balance_pgdat mm/vmscan.c:7124 [inline]
 kswapd+0x147c/0x2800 mm/vmscan.c:7389
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff88801fef60f8
 which belongs to the cache jfs_mp of size 184
The buggy address is located 40 bytes inside of
 freed 184-byte region [ffff88801fef60f8, ffff88801fef61b0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1fef6
anon flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff8880328a6dc0 ffffea000045e380 dead000000000009
raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2800(GFP_NOWAIT|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5825, tgid 5824 (syz.0.19), ts 160783556802, free_ts 160194828150
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x234/0x290 mm/page_alloc.c:1845
 prep_new_page mm/page_alloc.c:1853 [inline]
 get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3879
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5178
 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_noprof+0x3f9/0x6e0 mm/slub.c:5295
 mempool_alloc_noprof+0x1a7/0x510 mm/mempool.c:406
 alloc_metapage fs/jfs/jfs_metapage.c:264 [inline]
 __get_metapage+0x509/0xe20 fs/jfs/jfs_metapage.c:761
 diReadSpecial+0x25b/0x710 fs/jfs/jfs_imap.c:447
 jfs_mount+0x174/0x870 fs/jfs/jfs_mount.c:108
 jfs_fill_super+0x6bc/0xd80 fs/jfs/super.c:523
 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 15 tgid 15 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1394 [inline]
 __free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2901
 __tlb_remove_table_free mm/mmu_gather.c:227 [inline]
 tlb_remove_table_rcu+0x85/0x100 mm/mmu_gather.c:290
 rcu_do_batch kernel/rcu/tree.c:2605 [inline]
 rcu_core+0xcab/0x1770 kernel/rcu/tree.c:2861
 handle_softirqs+0x286/0x870 kernel/softirq.c:622
 run_ksoftirqd+0x9b/0x100 kernel/softirq.c:1063
 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
 kthread+0x711/0x8a0 kernel/kthread.c:463
 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:
 ffff88801fef6000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801fef6080: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fa
>ffff88801fef6100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff88801fef6180: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fa fb
 ffff88801fef6200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit:         8b690556 Merge tag 'for-linus' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16b89658580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8a9971d3cfd3619a
dashboard link: https://syzkaller.appspot.com/bug?extid=4c1966e88c28fa96e053
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=14b94e0a580000

Powered by blists - more mailing lists