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

Status: upstream: reported C repro on 2026/09/18 02:35
Reported-by: syzbot+d45c697a72906340529f@syzkaller.appspotmail.com
First crash: 47d, last: 29d
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/10/22 upstream (ToT) 7be4bc52fd9e C Didn't crash
▶ ▼ 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 20d 77d 26/29 upstream: reported C repro on 2026/08/19 05:22
linux-6.6 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug 17 13 29d 49d 0/2 upstream: reported on 2026/09/16 06:54
linux-5.15 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug 17 syz, C 51 29d 49d 0/3 upstream: reported C repro on 2026/09/16 06:37

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in string_nocheck lib/vsprintf.c:643 [inline]
BUG: KASAN: slab-out-of-bounds in string+0x204/0x290 lib/vsprintf.c:725
Read of size 1 at addr ffff8880562e69d0 by task syz.0.2756/17434

CPU: 0 PID: 17434 Comm: syz.0.2756 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 string_nocheck lib/vsprintf.c:643 [inline]
 string+0x204/0x290 lib/vsprintf.c:725
 vsnprintf+0x10db/0x1c20 lib/vsprintf.c:2805
 va_format lib/vsprintf.c:1685 [inline]
 pointer+0x870/0xfe0 lib/vsprintf.c:2436
 vsnprintf+0xd7c/0x1c20 lib/vsprintf.c:2809
 vprintk_store+0x3d7/0xcf0 kernel/printk/printk.c:2187
 vprintk_emit+0x114/0x6a0 kernel/printk/printk.c:2284
 _printk+0xda/0x130 kernel/printk/printk.c:2328
 __dynamic_pr_debug+0x196/0x240 lib/dynamic_debug.c:875
 idletimer_tg_checkentry_v1+0xc93/0xe20 net/netfilter/xt_IDLETIMER.c:353
 xt_check_target+0x49d/0xbf0 net/netfilter/x_tables.c:1061
 nft_target_init+0x678/0x9c0 net/netfilter/nft_compat.c:268
 nf_tables_newexpr net/netfilter/nf_tables_api.c:3076 [inline]
 nf_tables_newrule+0x170a/0x2810 net/netfilter/nf_tables_api.c:3808
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:519 [inline]
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:639 [inline]
 nfnetlink_rcv+0x1119/0x2470 net/netfilter/nfnetlink.c:657
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x7ad/0x920 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ad/0xbd0 net/netlink/af_netlink.c:1877
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 ____sys_sendmsg+0x5ed/0x9a0 net/socket.c:2519
 ___sys_sendmsg+0x2a2/0x360 net/socket.c:2573
 __sys_sendmsg net/socket.c:2602 [inline]
 __do_sys_sendmsg net/socket.c:2611 [inline]
 __se_sys_sendmsg+0x1c3/0x2b0 net/socket.c:2609
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd4ea19e199
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:00007fd4eb14d028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fd4ea425fa0 RCX: 00007fd4ea19e199
RDX: 0000000000000000 RSI: 0000200000000000 RDI: 0000000000000003
RBP: 00007fd4ea2358e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd4ea426038 R14: 00007fd4ea425fa0 R15: 00007ffe380c6b68
 </TASK>

Allocated by task 17434:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 __do_kmalloc_node mm/slab_common.c:936 [inline]
 __kmalloc+0xb3/0x240 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 nf_tables_newrule+0x14d9/0x2810 net/netfilter/nf_tables_api.c:3790
 nfnetlink_rcv_batch net/netfilter/nfnetlink.c:519 [inline]
 nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:639 [inline]
 nfnetlink_rcv+0x1119/0x2470 net/netfilter/nfnetlink.c:657
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x7ad/0x920 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ad/0xbd0 net/netlink/af_netlink.c:1877
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 ____sys_sendmsg+0x5ed/0x9a0 net/socket.c:2519
 ___sys_sendmsg+0x2a2/0x360 net/socket.c:2573
 __sys_sendmsg net/socket.c:2602 [inline]
 __do_sys_sendmsg net/socket.c:2611 [inline]
 __se_sys_sendmsg+0x1c3/0x2b0 net/socket.c:2609
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff8880562e6980
 which belongs to the cache kmalloc-cg-96 of size 96
The buggy address is located 80 bytes inside of
 96-byte region [ffff8880562e6980, ffff8880562e69e0)

The buggy address belongs to the physical page:
page:ffffea000158b980 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x562e6
memcg:ffff8880268aaa01
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea0001d13100 dead000000000002 ffff8880174428c0
raw: 0000000000000000 0000000080200020 00000001ffffffff ffff8880268aaa01
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 6680, tgid 6680 (syz.3.494), ts 258233854847, free_ts 258181990211
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2560
 prep_new_page mm/page_alloc.c:2567 [inline]
 get_page_from_freelist+0x206b/0x2180 mm/page_alloc.c:4358
 __alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5658
 alloc_slab_page+0x5d/0x180 mm/slub.c:1799
 allocate_slab mm/slub.c:1944 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:1997
 ___slab_alloc+0xbc5/0x1240 mm/slub.c:3154
 __slab_alloc mm/slub.c:3240 [inline]
 slab_alloc_node mm/slub.c:3325 [inline]
 __kmem_cache_alloc_node+0x126/0x270 mm/slub.c:3398
 kmalloc_trace+0x26/0xe0 mm/slab_common.c:1026
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 get_undo_list ipc/sem.c:1856 [inline]
 copy_semundo+0xb2/0x230 ipc/sem.c:2314
 copy_process+0x17e3/0x4070 kernel/fork.c:2343
 kernel_clone+0x24b/0x900 kernel/fork.c:2765
 __do_sys_clone3 kernel/fork.c:3064 [inline]
 __se_sys_clone3+0x32d/0x3f0 kernel/fork.c:3048
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1487 [inline]
 free_pcp_prepare mm/page_alloc.c:1537 [inline]
 free_unref_page_prepare+0x8e5/0x9e0 mm/page_alloc.c:3414
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3509
 free_slab mm/slub.c:2036 [inline]
 discard_slab mm/slub.c:2042 [inline]
 __unfreeze_partials+0x188/0x1e0 mm/slub.c:2591
 put_cpu_partial+0x17c/0x250 mm/slub.c:2667
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x490 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 __kmem_cache_alloc_node+0x19d/0x270 mm/slub.c:3398
 kmalloc_trace+0x26/0xe0 mm/slab_common.c:1026
 kmalloc include/linux/slab.h:563 [inline]
 netdev_name_node_alloc net/core/dev.c:259 [inline]
 netdev_name_node_head_alloc net/core/dev.c:273 [inline]
 register_netdevice+0x555/0x1b80 net/core/dev.c:10163
 veth_newlink+0x8be/0xd60 drivers/net/veth.c:1772
 rtnl_newlink_create net/core/rtnetlink.c:3436 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3656 [inline]
 rtnl_newlink+0x14b3/0x1f90 net/core/rtnetlink.c:3669
 rtnetlink_rcv_msg+0x863/0xfb0 net/core/rtnetlink.c:6166
 netlink_rcv_skb+0x1ef/0x440 net/netlink/af_netlink.c:2516
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x7ad/0x920 net/netlink/af_netlink.c:1344

Memory state around the buggy address:
 ffff8880562e6880: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
 ffff8880562e6900: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff8880562e6980: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
                                                 ^
 ffff8880562e6a00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff8880562e6a80: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================

Crashes (18):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/06 12:19 linux-6.1.y a500ba24937a f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/10/02 10:46 linux-6.1.y 1a8763b93150 6d32eb1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/29 19:55 linux-6.1.y 1a8763b93150 328436b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/29 19:55 linux-6.1.y 1a8763b93150 328436b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/29 03:59 linux-6.1.y 1a8763b93150 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/29 03:59 linux-6.1.y 1a8763b93150 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/23 00:03 linux-6.1.y 1a8763b93150 5207b90e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/21 19:48 linux-6.1.y 1a8763b93150 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/10/06 08:17 linux-6.1.y a500ba24937a f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/10/01 09:12 linux-6.1.y 1a8763b93150 38f7f0d1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/27 23:37 linux-6.1.y 1a8763b93150 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/27 23:35 linux-6.1.y 1a8763b93150 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/26 22:11 linux-6.1.y 1a8763b93150 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/26 22:10 linux-6.1.y 1a8763b93150 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/21 17:09 linux-6.1.y 1a8763b93150 853b104b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/21 14:10 linux-6.1.y 1a8763b93150 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/20 19:32 linux-6.1.y 1a8763b93150 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/18 02:35 linux-6.1.y 1a8763b93150 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
* Struck through repros no longer work on HEAD.