[moderation] [nbd?] KASAN: slab-use-after-free Write in recv_work (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0d97f2067c16 Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17916304580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f47338d36b741532
dashboard link: https://syzkaller.appspot.com/bug?extid=1824722b5f062ae66812
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [ax...@kernel.dk jo...@toxicpanda.com linux...@vger.kernel.org linux-...@vger.kernel.org n...@other.debian.org]

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-0d97f206.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/00c28e18345f/vmlinux-0d97f206.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ffcfd6164d80/bzImage-0d97f206.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+182472...@syzkaller.appspotmail.com

Bluetooth: hci0: command tx timeout
==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_dec include/linux/atomic/atomic-instrumented.h:592 [inline]
BUG: KASAN: slab-use-after-free in recv_work+0x215e/0x24f0 drivers/block/nbd.c:1022
Write of size 4 at addr ffff88800b5c7a78 by task kworker/u5:2/5308

CPU: 0 UID: 0 PID: 5308 Comm: kworker/u5:2 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
Workqueue: nbd0-recv recv_work
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
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:200
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
atomic_dec include/linux/atomic/atomic-instrumented.h:592 [inline]
recv_work+0x215e/0x24f0 drivers/block/nbd.c:1022
process_one_work kernel/workqueue.c:3263 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
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
</TASK>

Allocated by task 5331:
kasan_save_stack mm/kasan/common.c:56 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:417
kasan_kmalloc include/linux/kasan.h:262 [inline]
__kmalloc_cache_noprof+0x3d5/0x6f0 mm/slub.c:5724
kmalloc_noprof include/linux/slab.h:957 [inline]
kzalloc_noprof include/linux/slab.h:1094 [inline]
nbd_alloc_and_init_config+0x88/0x260 drivers/block/nbd.c:1677
nbd_genl_connect+0x9d7/0x18f0 drivers/block/nbd.c:2139
genl_family_rcv_msg_doit+0x215/0x300 net/netlink/genetlink.c:1115
genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210
netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2552
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg+0x21c/0x270 net/socket.c:742
____sys_sendmsg+0x505/0x830 net/socket.c:2630
___sys_sendmsg+0x21f/0x2a0 net/socket.c:2684
__sys_sendmsg net/socket.c:2716 [inline]
__do_sys_sendmsg net/socket.c:2721 [inline]
__se_sys_sendmsg net/socket.c:2719 [inline]
__x64_sys_sendmsg+0x19b/0x260 net/socket.c:2719
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 5308:
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:2514 [inline]
slab_free mm/slub.c:6566 [inline]
kfree+0x19a/0x6d0 mm/slub.c:6773
nbd_config_put+0x642/0x790 drivers/block/nbd.c:1457
recv_work+0x2148/0x24f0 drivers/block/nbd.c:1021
process_one_work kernel/workqueue.c:3263 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
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 ffff88800b5c7a00
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 120 bytes inside of
freed 256-byte region [ffff88800b5c7a00, ffff88800b5c7b00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xb5c7
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801a441b40 dead000000000100 dead000000000122
raw: 0000000000000000 0000000080080008 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 0x252800(GFP_NOWAIT|__GFP_NORETRY|__GFP_COMP|__GFP_THISNODE), pid 4719, tgid 4719 (udevd), ts 84765823033, free_ts 42600834818
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+0x2365/0x2440 mm/page_alloc.c:3884
__alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5183
alloc_slab_page mm/slub.c:3032 [inline]
allocate_slab+0x71/0x3a0 mm/slub.c:3203
new_slab mm/slub.c:3257 [inline]
___slab_alloc+0xe94/0x1920 mm/slub.c:4627
__slab_alloc+0x65/0x100 mm/slub.c:4746
__slab_alloc_node mm/slub.c:4822 [inline]
slab_alloc_node mm/slub.c:5233 [inline]
__do_kmalloc_node mm/slub.c:5602 [inline]
__kmalloc_node_noprof+0x5cc/0x800 mm/slub.c:5609
kmalloc_array_node_noprof include/linux/slab.h:1075 [inline]
alloc_slab_obj_exts mm/slub.c:2115 [inline]
account_slab mm/slub.c:3157 [inline]
allocate_slab+0x179/0x3a0 mm/slub.c:3222
new_slab mm/slub.c:3257 [inline]
___slab_alloc+0xe94/0x1920 mm/slub.c:4627
__slab_alloc+0x65/0x100 mm/slub.c:4746
__slab_alloc_node mm/slub.c:4822 [inline]
slab_alloc_node mm/slub.c:5233 [inline]
kmem_cache_alloc_lru_noprof+0x3ef/0x6d0 mm/slub.c:5264
alloc_inode+0xb8/0x1b0 fs/inode.c:348
iget_locked+0x106/0x580 fs/inode.c:1445
kernfs_get_inode+0x4f/0x780 fs/kernfs/inode.c:253
kernfs_iop_lookup+0x1f6/0x320 fs/kernfs/dir.c:1236
__lookup_slow+0x294/0x3d0 fs/namei.c:1816
page last free pid 29 tgid 29 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:2906
__folio_put+0x21b/0x2c0 mm/swap.c:112
migrate_folio_move mm/migrate.c:1404 [inline]
migrate_folios_move mm/migrate.c:1713 [inline]
migrate_pages_batch+0x22a3/0x35e0 mm/migrate.c:1969
migrate_pages_sync mm/migrate.c:1999 [inline]
migrate_pages+0x1bcc/0x2930 mm/migrate.c:2108
compact_zone+0x23e1/0x4ab0 mm/compaction.c:2647
compact_node+0x1d2/0x280 mm/compaction.c:2916
kcompactd+0xbc8/0x1290 mm/compaction.c:3214
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:
ffff88800b5c7900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88800b5c7980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88800b5c7a00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88800b5c7a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88800b5c7b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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