KASAN: slab-use-after-free Write in recv_work (3)

Status: fixed on 2026/01/07 12:29
Subsystems: nbd
[Documentation on labels]
Reported-by: syzbot+56fbf4c7ddf65e95c7cc@syzkaller.appspotmail.com
Fix commit: 9517b82d8d42 nbd: defer config put in recv_work
First crash: 288d, last: 235d
▶ ▼ Discussions (4)
Title Replies (including bot) Last reply
Re: [PATCH v6] mm/hugetlb: ignore hugepage kernel args if hugepages are unsupported 2 (2) 2025/12/23 05:48
[PATCH] nbd: defer config put in recv_work 3 (3) 2025/11/10 04:05
[syzbot] [nbd?] KASAN: slab-use-after-free Write in recv_work (3) 0 (6) 2025/11/07 01:19
[syzbot] Monthly nbd report (Nov 2025) 0 (1) 2025/11/04 14:21
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 KASAN: slab-use-after-free Write in recv_work origin:upstream missing-backport 22 C error 2 214d 263d 0/2 upstream: reported C repro on 2025/11/03 02:12
upstream KASAN: slab-use-after-free Write in recv_work (2) nbd 22 C 16 341d 437d 29/29 fixed on 2025/09/04 16:57
upstream KASAN: slab-use-after-free Write in recv_work nbd 22 10 447d 587d 28/29 fixed on 2025/05/06 15:33
upstream KASAN: use-after-free Read in recv_work nbd 19 1 2001d 1997d 0/29 auto-closed as invalid on 2021/03/30 16:37
upstream KASAN: use-after-free Read in recv_work (2) nbd 19 1 1638d 1633d 0/29 auto-closed as invalid on 2022/05/27 07:10
▶ ▼ Last patch testing requests (5)
Created Duration User Patch Repo Result
2025/11/07 01:18 1h02m lizhi.xu@windriver.com patch linux-next OK log
2025/11/05 14:40 25m eslam.medhat1993@gmail.com patch linux-next OK log
2025/11/03 06:44 7m lizhi.xu@windriver.com patch linux-next error
2025/11/03 05:49 1m lizhi.xu@windriver.com patch linux-next error
2025/11/03 02:10 23m lizhi.xu@windriver.com patch linux-next report log

Sample crash report:
block nbd0: Receive control failed (result -32)
block nbd0: shutting down sockets
==================================================================
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+0x1b78/0x1c60 drivers/block/nbd.c:1028
Write of size 4 at addr ffff88802f2bee78 by task kworker/u9:1/5145

CPU: 0 UID: 0 PID: 5145 Comm: kworker/u9:1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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+0x1b78/0x1c60 drivers/block/nbd.c:1028
 process_one_work+0x94a/0x15d0 kernel/workqueue.c:3267
 process_scheduled_works kernel/workqueue.c:3350 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3431
 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 5998:
 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:397 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:414
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __kmalloc_cache_noprof+0x3e2/0x700 mm/slub.c:5771
 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:1683
 nbd_genl_connect+0x9d7/0x18f0 drivers/block/nbd.c:2145
 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:2550
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:746
 ____sys_sendmsg+0x505/0x830 net/socket.c:2634
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2688
 __sys_sendmsg net/socket.c:2720 [inline]
 __do_sys_sendmsg net/socket.c:2725 [inline]
 __se_sys_sendmsg net/socket.c:2723 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2723
 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 5145:
 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:584
 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:2547 [inline]
 slab_free mm/slub.c:6638 [inline]
 kfree+0x19a/0x6d0 mm/slub.c:6845
 nbd_config_put+0x4a1/0x580 drivers/block/nbd.c:1463
 recv_work+0x1b62/0x1c60 drivers/block/nbd.c:1027
 process_one_work+0x94a/0x15d0 kernel/workqueue.c:3267
 process_scheduled_works kernel/workqueue.c:3350 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3431
 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 ffff88802f2bee00
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 120 bytes inside of
 freed 256-byte region [ffff88802f2bee00, ffff88802f2bef00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2f2be
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b026b40 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b026b40 dead000000000122 0000000000000000
head: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffea0000bcaf81 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 5937, tgid 5937 (syz-executor), ts 108999640718, free_ts 108976063617
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3920
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5214
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2479
 alloc_slab_page mm/slub.c:3063 [inline]
 allocate_slab+0x96/0x350 mm/slub.c:3236
 new_slab mm/slub.c:3290 [inline]
 ___slab_alloc+0xe94/0x18a0 mm/slub.c:4659
 __slab_alloc+0x65/0x100 mm/slub.c:4778
 __slab_alloc_node mm/slub.c:4854 [inline]
 slab_alloc_node mm/slub.c:5276 [inline]
 __do_kmalloc_node mm/slub.c:5649 [inline]
 __kmalloc_noprof+0x47d/0x800 mm/slub.c:5662
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kmalloc_array_noprof include/linux/slab.h:1003 [inline]
 genl_family_rcv_msg_attrs_parse+0xa3/0x2a0 net/netlink/genetlink.c:940
 genl_family_rcv_msg_doit+0xb8/0x300 net/netlink/genetlink.c:1093
 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:2550
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:746
page last free pid 5937 tgid 5937 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 __free_frozen_pages+0xbc8/0xd30 mm/page_alloc.c:2948
 __slab_free+0x2e7/0x390 mm/slub.c:5970
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:349
 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+0x37d/0x700 mm/slub.c:5295
 __kernfs_new_node+0xd7/0x7e0 fs/kernfs/dir.c:637
 kernfs_new_node+0x102/0x210 fs/kernfs/dir.c:713
 __kernfs_create_file+0x4b/0x2e0 fs/kernfs/file.c:1057
 sysfs_add_file_mode_ns+0x238/0x300 fs/sysfs/file.c:313
 sysfs_merge_group+0x177/0x310 fs/sysfs/group.c:376
 dpm_sysfs_add+0xd2/0x270 drivers/base/power/sysfs.c:704
 device_add+0x4d8/0xb80 drivers/base/core.c:3649
 wiphy_register+0x1d2e/0x2d20 net/wireless/core.c:1035
 ieee80211_register_hw+0x34a7/0x4110 net/mac80211/main.c:1591
 mac80211_hwsim_new_radio+0x2f85/0x5340 drivers/net/wireless/virtual/mac80211_hwsim.c:5804

Memory state around the buggy address:
 ffff88802f2bed00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802f2bed80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802f2bee00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff88802f2bee80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802f2bef00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/02 23:47 linux-next 98bd8b16ae57 2c50b6a9 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Write in recv_work
2025/11/30 16:32 upstream 6bda50f4333f d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Write in recv_work
2025/11/13 00:55 upstream 24172e0d7990 07e030de .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Write in recv_work
2025/10/08 06:38 upstream 0d97f2067c16 7e2882b3 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Write in recv_work
2025/11/02 23:40 upstream 6146a0f1dfae 2c50b6a9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Write in recv_work
2025/11/02 22:50 linux-next 98bd8b16ae57 2c50b6a9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce KASAN: slab-use-after-free Write in recv_work
* Struck through repros no longer work on HEAD.