[moderation] [jfs?] KASAN: slab-use-after-free Write in lmLogSync

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May 28, 2026, 6:57:32 PM (16 hours ago) May 28
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Hello,

syzbot found the following issue on:

HEAD commit: 6a97c4d5262d Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10c04d36580000
kernel config: https://syzkaller.appspot.com/x/.config?x=67ffb7a3dae3b364
dashboard link: https://syzkaller.appspot.com/bug?extid=e9340470d12334b79a08
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
CC: [jfs-dis...@lists.sourceforge.net linux-...@vger.kernel.org sha...@kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/27fccab6d587/disk-6a97c4d5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4e2627cdbafb/vmlinux-6a97c4d5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/061ff801444b/bzImage-6a97c4d5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e93404...@syzkaller.appspotmail.com

... Log Wrap ... Log Wrap ... Log Wrap ...
==================================================================
BUG: KASAN: slab-use-after-free in lmLogSync+0x794/0x7b0 fs/jfs/jfs_logmgr.c:1003
Write of size 4 at addr ffff88807d709218 by task jfsCommit/117

CPU: 0 UID: 0 PID: 117 Comm: jfsCommit Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0x13d/0x4b0 mm/kasan/report.c:482
kasan_report+0xdf/0x1d0 mm/kasan/report.c:595
lmLogSync+0x794/0x7b0 fs/jfs/jfs_logmgr.c:1003
jfs_syncpt+0x89/0xa0 fs/jfs/jfs_logmgr.c:1039
txEnd+0x318/0x490 fs/jfs/jfs_txnmgr.c:551
txLazyCommit fs/jfs/jfs_txnmgr.c:2686 [inline]
jfs_lazycommit+0x748/0xab0 fs/jfs/jfs_txnmgr.c:2735
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>

Allocated by task 15951:
kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
kmalloc_noprof include/linux/slab.h:950 [inline]
kzalloc_noprof include/linux/slab.h:1188 [inline]
open_inline_log fs/jfs/jfs_logmgr.c:1157 [inline]
lmLogOpen+0x571/0x1360 fs/jfs/jfs_logmgr.c:1067
jfs_mount_rw+0x2e0/0x690 fs/jfs/jfs_mount.c:257
jfs_fill_super+0xbc0/0xf50 fs/jfs/super.c:532
get_tree_bdev_flags+0x38c/0x620 fs/super.c:1694
vfs_get_tree+0x92/0x320 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3758 [inline]
do_new_mount fs/namespace.c:3834 [inline]
path_mount+0x7d0/0x23d0 fs/namespace.c:4154
do_mount fs/namespace.c:4167 [inline]
__do_sys_mount fs/namespace.c:4383 [inline]
__se_sys_mount fs/namespace.c:4360 [inline]
__x64_sys_mount+0x293/0x310 fs/namespace.c:4360
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x10b/0x860 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 10281:
kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2689 [inline]
slab_free mm/slub.c:6251 [inline]
kfree+0x223/0x6c0 mm/slub.c:6566
lmLogClose+0x55f/0x6f0 fs/jfs/jfs_logmgr.c:1458
jfs_umount+0x30c/0x430 fs/jfs/jfs_umount.c:124
jfs_put_super+0x88/0x1a0 fs/jfs/super.c:194
generic_shutdown_super+0x167/0x360 fs/super.c:646
kill_block_super+0x3b/0xa0 fs/super.c:1725
deactivate_locked_super+0xc1/0x1b0 fs/super.c:476
deactivate_super fs/super.c:509 [inline]
deactivate_super+0xe7/0x110 fs/super.c:505
cleanup_mnt+0x21f/0x450 fs/namespace.c:1312
task_work_run+0x150/0x240 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
exit_to_user_mode_loop+0x107/0x4f0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
do_syscall_64+0x706/0x860 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807d709000
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 536 bytes inside of
freed 1024-byte region [ffff88807d709000, ffff88807d709400)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88807d70d000 pfn:0x7d708
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff88813fe34dc0 ffffea0001ddac10 ffffea0001e99e10
raw: ffff88807d70d000 000000080010000e 00000000f5000000 0000000000000000
head: 00fff00000000240 ffff88813fe34dc0 ffffea0001ddac10 ffffea0001e99e10
head: ffff88807d70d000 000000080010000e 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 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 Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5636, tgid 5636 (syz-executor), ts 92244588377, free_ts 92228867410
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1858
prep_new_page mm/page_alloc.c:1866 [inline]
get_page_from_freelist+0x11a6/0x33b0 mm/page_alloc.c:3946
__alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5226
alloc_slab_page mm/slub.c:3278 [inline]
allocate_slab mm/slub.c:3467 [inline]
new_slab+0xa6/0x6c0 mm/slub.c:3525
refill_objects+0x277/0x420 mm/slub.c:7272
refill_sheaf mm/slub.c:2816 [inline]
__pcs_replace_empty_main+0x375/0x650 mm/slub.c:4652
alloc_from_pcs mm/slub.c:4750 [inline]
slab_alloc_node mm/slub.c:4884 [inline]
__do_kmalloc_node mm/slub.c:5295 [inline]
__kvmalloc_node_noprof+0x7da/0xa00 mm/slub.c:6833
bucket_table_alloc.isra.0+0x88/0x460 lib/rhashtable.c:194
rhashtable_init_noprof+0x43b/0x890 lib/rhashtable.c:1108
ipc_init_ids+0x92/0x280 ipc/util.c:120
create_ipc_ns ipc/namespace.c:89 [inline]
copy_ipcs+0x5c8/0x7e0 ipc/namespace.c:116
create_new_namespaces+0x20a/0xac0 kernel/nsproxy.c:112
unshare_nsproxy_namespaces+0xf2/0x220 kernel/nsproxy.c:234
ksys_unshare+0x438/0xab0 kernel/fork.c:3243
__do_sys_unshare kernel/fork.c:3317 [inline]
__se_sys_unshare kernel/fork.c:3315 [inline]
__x64_sys_unshare+0x31/0x40 kernel/fork.c:3315
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x10b/0x860 arch/x86/entry/syscall_64.c:94
page last free pid 5646 tgid 5646 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1402 [inline]
__free_frozen_pages+0x747/0x1040 mm/page_alloc.c:2943
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x47/0xf0 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4570 [inline]
slab_alloc_node mm/slub.c:4899 [inline]
__kmalloc_cache_noprof+0x243/0x6f0 mm/slub.c:5415
kmalloc_noprof include/linux/slab.h:950 [inline]
kzalloc_noprof include/linux/slab.h:1188 [inline]
hci_chan_create+0xa6/0x410 net/bluetooth/hci_conn.c:2874
l2cap_conn_add.part.0+0x1a/0xb00 net/bluetooth/l2cap_core.c:6997
l2cap_conn_add net/bluetooth/l2cap_core.c:69 [inline]
l2cap_connect_cfm+0x43e/0xf80 net/bluetooth/l2cap_core.c:7378
hci_connect_cfm include/net/bluetooth/hci_core.h:2139 [inline]
le_conn_complete_evt+0x197c/0x1f60 net/bluetooth/hci_event.c:5865
hci_le_conn_complete_evt+0x23c/0x3a0 net/bluetooth/hci_event.c:5891
hci_le_meta_evt+0x34a/0x5f0 net/bluetooth/hci_event.c:7529
hci_event_func net/bluetooth/hci_event.c:7793 [inline]
hci_event_packet+0x51c/0xcd0 net/bluetooth/hci_event.c:7847
hci_rx_work+0x451/0xfc0 net/bluetooth/hci_core.c:4077
process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314
process_scheduled_works kernel/workqueue.c:3397 [inline]
worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478
kthread+0x370/0x450 kernel/kthread.c:436

Memory state around the buggy address:
ffff88807d709100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807d709180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807d709200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88807d709280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88807d709300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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