KASAN: slab-out-of-bounds Read in __dynamic_pr_debug

Status: upstream: reported on 2026/09/16 06:54
Reported-by: syzbot+bf5d3c048e61b09c026e@syzkaller.appspotmail.com
First crash: 46d, last: 26d
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-out-of-bounds Read in __dynamic_pr_debug prio:high net nfc 17 syz, C 453 17d 74d 26/29 upstream: reported C repro on 2026/08/19 05:22
linux-5.15 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug 17 syz, C 51 26d 46d 0/3 upstream: reported C repro on 2026/09/16 06:37
linux-6.1 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug 17 syz, C 18 26d 45d 0/3 upstream: reported C repro on 2026/09/18 02:35

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in string_nocheck lib/vsprintf.c:645 [inline]
BUG: KASAN: slab-out-of-bounds in string+0x204/0x290 lib/vsprintf.c:727
Read of size 1 at addr ffff88802c3fb450 by task syz.2.2293/13078

CPU: 0 PID: 13078 Comm: syz.2.2293 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 string_nocheck lib/vsprintf.c:645 [inline]
 string+0x204/0x290 lib/vsprintf.c:727
 vsnprintf+0xf72/0x1ba0 lib/vsprintf.c:2823
 va_format lib/vsprintf.c:1682 [inline]
 pointer+0x9ed/0x1150 lib/vsprintf.c:2454
 vsnprintf+0xdaa/0x1ba0 lib/vsprintf.c:2827
 vprintk_store+0x3d9/0xd50 kernel/printk/printk.c:2226
 vprintk_emit+0x117/0x610 kernel/printk/printk.c:2322
 _printk+0xde/0x130 kernel/printk/printk.c:2366
 __dynamic_pr_debug+0x1a3/0x260 lib/dynamic_debug.c:879
 idletimer_tg_checkentry_v1+0xc97/0xe20 net/netfilter/xt_IDLETIMER.c:353
 xt_check_target+0x4a1/0xbf0 net/netfilter/x_tables.c:1061
 nft_target_init+0x694/0xa00 net/netfilter/nft_compat.c:268
 nf_tables_newexpr net/netfilter/nf_tables_api.c:3257 [inline]
 nf_tables_newrule+0x176e/0x2870 net/netfilter/nf_tables_api.c:4089
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:519 [inline]
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:639 [inline]
 nfnetlink_rcv+0x1133/0x2490 net/netfilter/nfnetlink.c:657
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x7b1/0x930 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x61b/0x980 net/socket.c:2595
 ___sys_sendmsg+0x2a6/0x360 net/socket.c:2649
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2687 [inline]
 __se_sys_sendmsg+0x1d0/0x2c0 net/socket.c:2685
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe08419e199
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe08509a028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fe084425fa0 RCX: 00007fe08419e199
RDX: 0000000000000000 RSI: 0000200000000000 RDI: 0000000000000003
RBP: 00007fe0842358e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe084426038 R14: 00007fe084425fa0 R15: 00007ffc13452958
 </TASK>

Allocated by task 13078:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc+0xb7/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 nf_tables_newrule+0x1515/0x2870 net/netfilter/nf_tables_api.c:4071
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:519 [inline]
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:639 [inline]
 nfnetlink_rcv+0x1133/0x2490 net/netfilter/nfnetlink.c:657
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x7b1/0x930 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x61b/0x980 net/socket.c:2595
 ___sys_sendmsg+0x2a6/0x360 net/socket.c:2649
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2687 [inline]
 __se_sys_sendmsg+0x1d0/0x2c0 net/socket.c:2685
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 __call_rcu_common kernel/rcu/tree.c:2721 [inline]
 call_rcu+0x153/0x900 kernel/rcu/tree.c:2837
 nf_unregister_net_hook net/netfilter/core.c:-1 [inline]
 nf_unregister_net_hooks+0xcb/0x130 net/netfilter/core.c:613
 nf_ct_netns_do_put net/netfilter/nf_conntrack_proto.c:549 [inline]
 nf_ct_netns_put+0x36d/0x520 net/netfilter/nf_conntrack_proto.c:-1
 nf_conncount_destroy+0x41/0x150 net/netfilter/nf_conncount.c:687
 ovs_ct_limit_exit_finish net/openvswitch/conntrack.c:1626 [inline]
 ovs_ct_exit_finish+0xa5/0x210 net/openvswitch/conntrack.c:2050
 ovs_exit_net+0xed/0x7a0 net/openvswitch/datapath.c:2751
 ops_exit_list net/core/net_namespace.c:173 [inline]
 cleanup_net+0x6f7/0xb00 net/core/net_namespace.c:656
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Second to last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 __call_rcu_common kernel/rcu/tree.c:2721 [inline]
 call_rcu+0x153/0x900 kernel/rcu/tree.c:2837
 nf_hook_entries_free net/netfilter/core.c:88 [inline]
 __nf_register_net_hook+0x787/0x910 net/netfilter/core.c:457
 nf_register_net_hook+0xb2/0x190 net/netfilter/core.c:578
 nf_register_net_hooks+0x44/0x1b0 net/netfilter/core.c:594
 brnf_device_event+0x132/0x1d0 net/bridge/br_netfilter_hooks.c:1129
 notifier_call_chain+0x18f/0x380 kernel/notifier.c:93
 call_netdevice_notifiers_extack net/core/dev.c:2077 [inline]
 call_netdevice_notifiers net/core/dev.c:2091 [inline]
 register_netdevice+0x1670/0x1ba0 net/core/dev.c:10375
 br_dev_newlink+0x27/0x110 net/bridge/br_netlink.c:1553
 rtnl_newlink_create net/core/rtnetlink.c:3529 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3749 [inline]
 rtnl_newlink+0x15a0/0x2170 net/core/rtnetlink.c:3762
 rtnetlink_rcv_msg+0x843/0xf90 net/core/rtnetlink.c:6484
 netlink_rcv_skb+0x235/0x4c0 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x7b1/0x930 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 __sys_sendto+0x4a9/0x6b0 net/socket.c:2201
 __do_sys_sendto net/socket.c:2213 [inline]
 __se_sys_sendto net/socket.c:2209 [inline]
 __x64_sys_sendto+0xde/0xf0 net/socket.c:2209
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88802c3fb400
 which belongs to the cache kmalloc-cg-96 of size 96
The buggy address is located 0 bytes to the right of
 allocated 80-byte region [ffff88802c3fb400, ffff88802c3fb450)

The buggy address belongs to the physical page:
page:ffffea0000b0fec0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2c3fb
memcg:ffff8880244f0e01
anon flags: 0xfff00000000800(slab|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000800 ffff888017c4db40 ffffea0001144a00 dead000000000005
raw: 0000000000000000 0000000080200020 00000001ffffffff ffff8880244f0e01
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, tgid 1 (swapper/0), ts 20470942461, free_ts 20463834241
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
 prep_new_page mm/page_alloc.c:1589 [inline]
 get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
 alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2118
 alloc_slab_page+0x5d/0x180 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253
 __slab_alloc mm/slub.c:3339 [inline]
 __slab_alloc_node mm/slub.c:3392 [inline]
 slab_alloc_node mm/slub.c:3485 [inline]
 __kmem_cache_alloc_node+0x11f/0x250 mm/slub.c:3534
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc+0xa7/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 __register_sysctl_table+0x71/0x1210 fs/proc/proc_sysctl.c:1373
 llc_sysctl_init+0x4e/0x80 net/llc/sysctl_net_llc.c:60
 llc2_init+0x5b/0x110 net/llc/af_llc.c:1270
 do_one_initcall+0x242/0x790 init/main.c:1210
 do_initcall_level+0x13d/0x1f0 init/main.c:1272
 do_initcalls+0x69/0xd0 init/main.c:1288
 kernel_init_freeable+0x3d9/0x560 init/main.c:1525
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 mm_free_pgd kernel/fork.c:811 [inline]
 __mmdrop+0xb4/0x3d0 kernel/fork.c:927
 free_bprm+0x144/0x390 fs/exec.c:1533
 kernel_execve+0x3e9/0x980 fs/exec.c:2079
 call_usermodehelper_exec_async+0x20b/0x350 kernel/umh.c:110
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Memory state around the buggy address:
 ffff88802c3fb300: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
 ffff88802c3fb380: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff88802c3fb400: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
                                                 ^
 ffff88802c3fb480: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff88802c3fb500: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================

Crashes (13):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/06 12:59 linux-6.6.y a91a6aa9253c f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/10/06 12:59 linux-6.6.y a91a6aa9253c f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/29 04:38 linux-6.6.y 79643295eba1 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/29 04:38 linux-6.6.y 79643295eba1 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/22 17:17 linux-6.6.y 79643295eba1 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/22 17:13 linux-6.6.y 79643295eba1 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/22 17:13 linux-6.6.y 79643295eba1 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/18 09:36 linux-6.6.y 79643295eba1 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/18 09:36 linux-6.6.y 79643295eba1 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/18 01:05 linux-6.6.y 79643295eba1 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/17 00:12 linux-6.6.y 79643295eba1 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/17 00:12 linux-6.6.y 79643295eba1 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/16 06:53 linux-6.6.y 79643295eba1 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
* Struck through repros no longer work on HEAD.