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

Status: upstream: reported on 2026/09/16 06:37
Reported-by: syzbot+d24bc1c42b24fc5b9447@syzkaller.appspotmail.com
First crash: 2d19h, last: 16h24m
▶ ▼ 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 142 1h07m 30d 0/29 upstream: reported C repro on 2026/08/19 05:22
linux-6.6 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug 17 6 16h48m 2d19h 0/2 upstream: reported on 2026/09/16 06:54
linux-6.1 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug 17 1 23h50m 23h50m 0/3 upstream: reported on 2026/09/18 02:35

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in string_nocheck lib/vsprintf.c:642 [inline]
BUG: KASAN: slab-out-of-bounds in string+0x204/0x290 lib/vsprintf.c:724
Read of size 1 at addr ffff8881435f2d99 by task syz.4.2416/13362

CPU: 1 PID: 13362 Comm: syz.4.2416 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 string_nocheck lib/vsprintf.c:642 [inline]
 string+0x204/0x290 lib/vsprintf.c:724
 vsnprintf+0x10db/0x1c20 lib/vsprintf.c:2811
 va_format lib/vsprintf.c:1713 [inline]
 pointer+0x7b2/0xc60 lib/vsprintf.c:2448
 vsnprintf+0xd7c/0x1c20 lib/vsprintf.c:2815
 vprintk_store+0x378/0x11b0 kernel/printk/printk.c:2164
 vprintk_emit+0x85/0x150 kernel/printk/printk.c:2258
 _printk+0xda/0x130 kernel/printk/printk.c:2299
 __dynamic_pr_debug+0x196/0x240 lib/dynamic_debug.c:619
 nfc_llcp_wks_sap net/nfc/llcp_core.c:344 [inline]
 nfc_llcp_get_sdp_ssap+0x3c1/0x3f0 net/nfc/llcp_core.c:420
 llcp_sock_bind+0x3a2/0x770 net/nfc/llcp_sock.c:117
 __sys_bind+0x2e9/0x3e0 net/socket.c:1730
 __do_sys_bind net/socket.c:1741 [inline]
 __se_sys_bind net/socket.c:1739 [inline]
 __x64_sys_bind+0x76/0x80 net/socket.c:1739
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7ffa7e4c3159
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:00007ffa7c71b028 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
RAX: ffffffffffffffda RBX: 00007ffa7e74afa0 RCX: 00007ffa7e4c3159
RDX: 0000000000000060 RSI: 0000200000000080 RDI: 0000000000000004
RBP: 00007ffa7e55a06b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffa7e74b038 R14: 00007ffa7e74afa0 R15: 00007ffeedd0f7e8
 </TASK>

Allocated by task 13362:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc mm/kasan/common.c:513 [inline]
 __kasan_kmalloc+0xaf/0xe0 mm/kasan/common.c:522
 kmemdup+0x22/0x50 mm/util.c:128
 llcp_sock_bind+0x360/0x770 net/nfc/llcp_sock.c:107
 __sys_bind+0x2e9/0x3e0 net/socket.c:1730
 __do_sys_bind net/socket.c:1741 [inline]
 __se_sys_bind net/socket.c:1739 [inline]
 __x64_sys_bind+0x76/0x80 net/socket.c:1739
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff8881435f2d98
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 1 bytes inside of
 8-byte region [ffff8881435f2d98, ffff8881435f2da0)
The buggy address belongs to the page:
page:ffffea00050d7c80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1435f2
flags: 0x57ff00000000200(slab|node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000200 0000000000000000 0000000100000001 ffff888016c41280
raw: 0000000000000000 0000000080660066 00000001ffffffff 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 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, ts 2421419469, free_ts 0
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x24f6/0x2670 mm/page_alloc.c:4192
 __alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
 alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2031
 alloc_slab_page mm/slub.c:1780 [inline]
 allocate_slab mm/slub.c:1917 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1980
 ___slab_alloc+0x807/0xdd0 mm/slub.c:3013
 __slab_alloc mm/slub.c:3100 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 slab_alloc mm/slub.c:3233 [inline]
 __kmalloc_track_caller+0x11b/0x330 mm/slub.c:4930
 kstrdup mm/util.c:60 [inline]
 kstrdup_const+0x51/0x90 mm/util.c:83
 kobject_set_name_vargs+0x5d/0x110 lib/kobject.c:297
 kobject_add_varg lib/kobject.c:392 [inline]
 kobject_init_and_add+0xeb/0x190 lib/kobject.c:481
 lookup_or_create_module_kobject+0xdf/0x160 kernel/params.c:762
 kernel_add_sysfs_param+0x1f/0x120 kernel/params.c:789
 param_sysfs_builtin+0x183/0x200 kernel/params.c:837
 param_sysfs_init+0x66/0x70 kernel/params.c:958
 do_one_initcall+0x272/0x730 init/main.c:1276
 do_initcall_level+0x13d/0x1f0 init/main.c:1349
 do_initcalls+0x4b/0x90 init/main.c:1365
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8881435f2c80: 05 fc fc fc fc fa fc fc fc fc fa fc fc fc fc fb
 ffff8881435f2d00: fc fc fc fc 05 fc fc fc fc fa fc fc fc fc 05 fc
>ffff8881435f2d80: fc fc fc 01 fc fc fc fc 05 fc fc fc fc fa fc fc
                            ^
 ffff8881435f2e00: fc fc 05 fc fc fc fc 05 fc fc fc fc fa fc fc fc
 ffff8881435f2e80: fc 07 fc fc fc fc 07 fc fc fc fc fa fc fc fc fc
==================================================================

Crashes (14):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/18 10:00 linux-5.15.y 0248c33e835e 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/17 23:29 linux-5.15.y 0248c33e835e 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/17 23:29 linux-5.15.y 0248c33e835e 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/17 21:59 linux-5.15.y 0248c33e835e 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/17 19:46 linux-5.15.y 0248c33e835e 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/17 19:46 linux-5.15.y 0248c33e835e 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/17 19:08 linux-5.15.y 0248c33e835e 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/17 19:08 linux-5.15.y 0248c33e835e 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/17 03:21 linux-5.15.y 0248c33e835e 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/16 09:40 linux-5.15.y 0248c33e835e 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/16 08:51 linux-5.15.y 0248c33e835e 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/16 08:51 linux-5.15.y 0248c33e835e 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/16 06:36 linux-5.15.y 0248c33e835e 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
2026/09/16 06:36 linux-5.15.y 0248c33e835e 12a0a44a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: slab-out-of-bounds Read in __dynamic_pr_debug
* Struck through repros no longer work on HEAD.