Re: [syzbot] [gfs2?] WARNING in gfs2_fill_super

syzbot
2026-03-25T00:00:03Z

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in gfs2_put_super

==================================================================
BUG: KASAN: slab-use-after-free in gfs2_put_super+0x83f/0x890 fs/gfs2/super.c:642
Read of size 1 at addr ffff888144ab83c0 by task syz-executor/6382

CPU: 1 UID: 0 PID: 6382 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description+0x55/0x1e0 mm/kasan/report.c:378
print_report+0x58/0x70 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
__kasan_check_byte+0x2a/0x40 mm/kasan/common.c:574
kasan_check_byte include/linux/kasan.h:402 [inline]
kmem_cache_destroy+0x21/0x170 mm/slab_common.c:531
gfs2_put_super+0x83f/0x890 fs/gfs2/super.c:642
generic_shutdown_super+0x13d/0x2d0 fs/super.c:646
kill_block_super+0x44/0x90 fs/super.c:1725
deactivate_locked_super+0xbc/0x130 fs/super.c:476
cleanup_mnt+0x437/0x4d0 fs/namespace.c:1312
task_work_run+0x1d9/0x270 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+0xed/0x480 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:269 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f52def9d9d7
Code: a2 c7 05 1c fd 24 00 00 00 00 00 eb 96 e8 e1 12 00 00 90 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007fff0f5bdd58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007f52df032050 RCX: 00007f52def9d9d7
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007fff0f5bde10
RBP: 00007fff0f5bde10 R08: 00007fff0f5bee10 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff0f5beea0
R13: 00007f52df032050 R14: 000000000001fbd6 R15: 00007fff0f5beee0
</TASK>

Allocated by task 6561:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
unpoison_slab_object mm/kasan/common.c:340 [inline]
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4569 [inline]
slab_alloc_node mm/slub.c:4898 [inline]
kmem_cache_alloc_noprof+0x2bc/0x650 mm/slub.c:4905
create_cache mm/slab_common.c:249 [inline]
__kmem_cache_create_args+0x2eb/0x440 mm/slab_common.c:380
__kmem_cache_create include/linux/slab.h:390 [inline]
gfs2_fill_super+0x13a4/0x21d0 fs/gfs2/ops_fstype.c:1202
get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1342
vfs_get_tree+0x92/0x2a0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3764 [inline]
do_new_mount+0x341/0xd30 fs/namespace.c:3840
do_mount fs/namespace.c:4173 [inline]
__do_sys_mount fs/namespace.c:4372 [inline]
__se_sys_mount+0x31d/0x420 fs/namespace.c:4349
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6382:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 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:2689 [inline]
slab_free mm/slub.c:6242 [inline]
kmem_cache_free+0x182/0x650 mm/slub.c:6369
kobject_cleanup lib/kobject.c:689 [inline]
kobject_release lib/kobject.c:720 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x228/0x560 lib/kobject.c:737
gfs2_kill_sb+0x435/0x450 fs/gfs2/ops_fstype.c:1806
deactivate_locked_super+0xbc/0x130 fs/super.c:476
cleanup_mnt+0x437/0x4d0 fs/namespace.c:1312
task_work_run+0x1d9/0x270 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+0xed/0x480 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:269 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888144ab83c0
which belongs to the cache kmem_cache of size 232
The buggy address is located 0 bytes inside of
freed 232-byte region [ffff888144ab83c0, ffff888144ab84a8)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888144ab8640 pfn:0x144ab8
flags: 0x57ff00000000200(workingset|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000200 ffff88813fea7000 ffffea000512ae50 ffff888140400108
raw: ffff888144ab8640 00000008000c0005 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 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid 1 (swapper/0), ts 24382700756, free_ts 6084051605
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x231/0x280 mm/page_alloc.c:1859
prep_new_page mm/page_alloc.c:1867 [inline]
get_page_from_freelist+0x2418/0x24b0 mm/page_alloc.c:3926
__alloc_frozen_pages_noprof+0x233/0x3d0 mm/page_alloc.c:5213
alloc_pages_mpol+0x235/0x490 mm/mempolicy.c:2484
alloc_slab_page mm/slub.c:3276 [inline]
allocate_slab+0x83/0x660 mm/slub.c:3467
new_slab mm/slub.c:3525 [inline]
___slab_alloc+0x154/0x6c0 mm/slub.c:4444
__slab_alloc_node mm/slub.c:4510 [inline]
slab_alloc_node mm/slub.c:4886 [inline]
kmem_cache_alloc_noprof+0x12d/0x650 mm/slub.c:4905
create_cache mm/slab_common.c:249 [inline]
__kmem_cache_create_args+0x2eb/0x440 mm/slab_common.c:380
__kmem_cache_create include/linux/slab.h:390 [inline]
btrfs_prelim_ref_init+0xad/0x110 fs/btrfs/backref.c:200
init_btrfs_fs+0x6d/0x1f0 fs/btrfs/super.c:2701
do_one_initcall+0x250/0x870 init/main.c:1384
do_initcall_level+0x104/0x190 init/main.c:1446
do_initcalls+0x59/0xa0 init/main.c:1462
kernel_init_freeable+0x2a6/0x3e0 init/main.c:1694
kernel_init+0x1d/0x1d0 init/main.c:1584
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
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:1403 [inline]
__free_frozen_pages+0xbc7/0xd30 mm/page_alloc.c:2944
vfree+0x1d1/0x2f0 mm/vmalloc.c:3472
free_partitions block/partitions/core.c:114 [inline]
check_partition block/partitions/core.c:173 [inline]
blk_add_partitions block/partitions/core.c:590 [inline]
bdev_disk_changed+0x923/0x1770 block/partitions/core.c:694
blkdev_get_whole+0x380/0x510 block/bdev.c:764
bdev_open+0x31e/0xd30 block/bdev.c:973
bdev_file_open_by_dev+0x1be/0x240 block/bdev.c:1075
disk_scan_partitions+0x1c1/0x2c0 block/genhd.c:387
add_disk_final block/genhd.c:416 [inline]
add_disk_fwnode+0x321/0x480 block/genhd.c:610
add_disk include/linux/blkdev.h:793 [inline]
brd_alloc+0x5b9/0x7c0 drivers/block/brd.c:340
brd_init+0xc1/0x120 drivers/block/brd.c:420
do_one_initcall+0x250/0x870 init/main.c:1384
do_initcall_level+0x104/0x190 init/main.c:1446
do_initcalls+0x59/0xa0 init/main.c:1462
kernel_init_freeable+0x2a6/0x3e0 init/main.c:1694
kernel_init+0x1d/0x1d0 init/main.c:1584
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158

Memory state around the buggy address:
ffff888144ab8280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888144ab8300: 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc
>ffff888144ab8380: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
^
ffff888144ab8400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888144ab8480: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Tested on:

commit: 85964cdc Add linux-next specific files for 20260324
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=146faa06580000
kernel config: https://syzkaller.appspot.com/x/.config?x=84ab18c6f45b39c
dashboard link: https://syzkaller.appspot.com/bug?extid=b441db1854c360b83221
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch: https://syzkaller.appspot.com/x/patch.diff?x=123a4b52580000