* KASAN: slab-use-after-free Read in jfs_lazycommit
@ 2026-06-26 21:27 sanan.hasanou
0 siblings, 0 replies; only message in thread
From: sanan.hasanou @ 2026-06-26 21:27 UTC (permalink / raw)
To: shaggy, brauner, mjguzik, ssrane_b23, jfs-discussion,
linux-kernel
Cc: syzkaller, contact
Good day, dear maintainers,
We found a bug using a modified version of syzkaller.
Kernel Branch: 7.0-rc1
Kernel Config: <https://drive.google.com/open?id=1sVxTU3tztwbXVxVud4pFzl2EIDdR3aOC>
Unfortunately, we don't have any reproducer for this bug yet.
Thank you!
Best regards,
Sanan Hasanov
==================================================================
BUG: KASAN: slab-use-after-free in jfs_lazycommit+0x74b/0xa90 fs/jfs/jfs_txnmgr.c:2737
Read of size 4 at addr ffff88806b71e894 by task jfsCommit/112
CPU: 1 UID: 0 PID: 112 Comm: jfsCommit Tainted: G L 7.0.0-rc1 #1 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 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
jfs_lazycommit+0x74b/0xa90 fs/jfs/jfs_txnmgr.c:2737
kthread+0x389/0x480 kernel/kthread.c:467
ret_from_fork+0x507/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:245
</TASK>
Allocated by task 32010:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x70 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xa0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__kmalloc_cache_noprof+0x325/0x680 mm/slub.c:5339
kmalloc_noprof include/linux/slab.h:962 [inline]
kzalloc_noprof include/linux/slab.h:1200 [inline]
jfs_fill_super+0xc2/0xd80 fs/jfs/super.c:452
get_tree_bdev_flags+0x402/0x4c0 fs/super.c:1694
vfs_get_tree+0x8c/0x2a0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3760 [inline]
do_new_mount+0x31a/0xce0 fs/namespace.c:3836
do_mount fs/namespace.c:4159 [inline]
__do_sys_mount fs/namespace.c:4348 [inline]
__se_sys_mount+0x313/0x400 fs/namespace.c:4325
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x160/0xfc0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x4b/0x53
Freed by task 23283:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x70 mm/kasan/common.c:78
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2687 [inline]
slab_free mm/slub.c:6124 [inline]
kfree+0x1c5/0x640 mm/slub.c:6442
generic_shutdown_super+0x137/0x2c0 fs/super.c:646
kill_block_super+0x44/0x90 fs/super.c:1725
deactivate_locked_super+0xb6/0x120 fs/super.c:476
cleanup_mnt+0x437/0x4d0 fs/namespace.c:1312
task_work_run+0x1ce/0x250 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+0xef/0x4e0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x33b/0xfc0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x4b/0x53
The buggy address belongs to the object at ffff88806b71e800
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 148 bytes inside of
freed 256-byte region [ffff88806b71e800, ffff88806b71e900)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88806b71fc00 pfn:0x6b71e
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x4fff00000000240(workingset|head|node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000240 ffff888018841b40 ffffea00011ed010 ffffea00016dd610
raw: ffff88806b71fc00 000000000010000a 00000000f5000000 0000000000000000
head: 04fff00000000240 ffff888018841b40 ffffea00011ed010 ffffea00016dd610
head: ffff88806b71fc00 000000000010000a 00000000f5000000 0000000000000000
head: 04fff00000000001 ffffea0001adc781 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 30812, tgid 30807 (syz.5.3073), ts 208748051074, free_ts 208732083627
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x238/0x290 mm/page_alloc.c:1889
prep_new_page mm/page_alloc.c:1897 [inline]
get_page_from_freelist+0x24e0/0x2570 mm/page_alloc.c:3962
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5250
alloc_slab_page mm/slub.c:3255 [inline]
allocate_slab+0x77/0x670 mm/slub.c:3444
new_slab mm/slub.c:3502 [inline]
refill_objects+0x33a/0x3d0 mm/slub.c:7134
refill_sheaf mm/slub.c:2804 [inline]
__pcs_replace_empty_main+0x2b6/0x620 mm/slub.c:4578
alloc_from_pcs mm/slub.c:4681 [inline]
slab_alloc_node mm/slub.c:4815 [inline]
__do_kmalloc_node mm/slub.c:5218 [inline]
__kmalloc_noprof+0x478/0x770 mm/slub.c:5231
kmalloc_noprof include/linux/slab.h:966 [inline]
kzalloc_noprof include/linux/slab.h:1200 [inline]
new_dir fs/proc/proc_sysctl.c:966 [inline]
get_subdir fs/proc/proc_sysctl.c:1010 [inline]
sysctl_mkdir_p fs/proc/proc_sysctl.c:1320 [inline]
__register_sysctl_table+0xba1/0x1340 fs/proc/proc_sysctl.c:1395
neigh_sysctl_register+0x9a2/0xa80 net/core/neighbour.c:3922
addrconf_sysctl_register+0xb3/0x1c0 net/ipv6/addrconf.c:7371
ipv6_add_dev+0xd21/0x13a0 net/ipv6/addrconf.c:459
addrconf_notify+0x771/0x1050 net/ipv6/addrconf.c:3654
notifier_call_chain+0x1b8/0x3f0 kernel/notifier.c:85
call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
call_netdevice_notifiers net/core/dev.c:2301 [inline]
register_netdevice+0x16f3/0x1ca0 net/core/dev.c:11449
tun_set_iff+0x83f/0xf00 drivers/net/tun.c:2807
__tun_chr_ioctl+0x783/0x1df0 drivers/net/tun.c:3088
page last free pid 30812 tgid 30807 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1433 [inline]
__free_frozen_pages+0xc3e/0xdd0 mm/page_alloc.c:2978
__slab_free+0x25e/0x2b0 mm/slub.c:5532
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4501 [inline]
slab_alloc_node mm/slub.c:4830 [inline]
__do_kmalloc_node mm/slub.c:5218 [inline]
__kmalloc_noprof+0x31b/0x770 mm/slub.c:5231
kmalloc_noprof include/linux/slab.h:966 [inline]
sk_prot_alloc+0xe7/0x210 net/core/sock.c:2245
sk_alloc+0x3a/0x380 net/core/sock.c:2301
tun_chr_open+0x7a/0x510 drivers/net/tun.c:3398
misc_open+0x2d8/0x340 drivers/char/misc.c:163
chrdev_open+0x4c8/0x5d0 fs/char_dev.c:411
do_dentry_open+0x77a/0x14d0 fs/open.c:949
vfs_open+0x3b/0x340 fs/open.c:1081
do_open fs/namei.c:4671 [inline]
path_openat+0x2d02/0x3740 fs/namei.c:4830
do_file_open+0x203/0x440 fs/namei.c:4859
do_sys_openat2+0x105/0x1e0 fs/open.c:1366
Memory state around the buggy address:
ffff88806b71e780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88806b71e800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88806b71e880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88806b71e900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88806b71e980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
<<<<<<<<<<<<<<< tail report >>>>>>>>>>>>>>>
raw: 04fff00000000240 ffff888018841b40 ffffea00011ed010 ffffea00016dd610
raw: ffff88806b71fc00 000000000010000a 00000000f5000000 0000000000000000
head: 04fff00000000240 ffff888018841b40 ffffea00011ed010 ffffea00016dd610
head: ffff88806b71fc00 000000000010000a 00000000f5000000 0000000000000000
head: 04fff00000000001 ffffea0001adc781 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 30812, tgid 30807 (syz.5.3073), ts 208748051074, free_ts 208732083627
post_alloc_hook+0x238/0x290
get_page_from_freelist+0x24e0/0x2570
__alloc_frozen_pages_noprof+0x181/0x370
allocate_slab+0x77/0x670
refill_objects+0x33a/0x3d0
__pcs_replace_empty_main+0x2b6/0x620
__kmalloc_noprof+0x478/0x770
__register_sysctl_table+0xba1/0x1340
neigh_sysctl_register+0x9a2/0xa80
addrconf_sysctl_register+0xb3/0x1c0
ipv6_add_dev+0xd21/0x13a0
addrconf_notify+0x771/0x1050
notifier_call_chain+0x1b8/0x3f0
register_netdevice+0x16f3/0x1ca0
tun_set_iff+0x83f/0xf00
__tun_chr_ioctl+0x783/0x1df0
page last free pid 30812 tgid 30807 stack trace:
__free_frozen_pages+0xc3e/0xdd0
__slab_free+0x25e/0x2b0
qlist_free_all+0x97/0x100
kasan_quarantine_reduce+0x143/0x160
__kasan_slab_alloc+0x22/0x80
__kmalloc_noprof+0x31b/0x770
sk_prot_alloc+0xe7/0x210
sk_alloc+0x3a/0x380
tun_chr_open+0x7a/0x510
misc_open+0x2d8/0x340
chrdev_open+0x4c8/0x5d0
do_dentry_open+0x77a/0x14d0
vfs_open+0x3b/0x340
path_openat+0x2d02/0x3740
do_file_open+0x203/0x440
do_sys_openat2+0x105/0x1e0
Memory state around the buggy address:
ffff88806b71e780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88806b71e800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88806b71e880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88806b71e900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88806b71e980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
Kernel panic - not syncing: KASAN: panic_on_warn set ...
CPU: 1 UID: 0 PID: 112 Comm: jfsCommit Tainted: G L 7.0.0-rc1 #1 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
vpanic+0x41f/0xa20
panic+0xb9/0xc0
check_panic_on_warn+0x84/0xa0
end_report+0x73/0x180
kasan_report+0x129/0x150
jfs_lazycommit+0x74b/0xa90
kthread+0x389/0x480
ret_from_fork+0x507/0xb90
ret_from_fork_asm+0x11/0x20
</TASK>
Kernel Offset: disabled
Rebooting in 86400 seconds..
<<<<<<<<<<<<<<< tail report >>>>>>>>>>>>>>>
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2026-06-26 21:27 KASAN: slab-use-after-free Read in jfs_lazycommit sanan.hasanou
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