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: 12d, last: 10h50m
▶ ▼ 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 432 1h16m 42d 21/29 upstream: reported C repro on 2026/08/19 05:22
linux-6.6 KASAN: slab-out-of-bounds Read in __dynamic_pr_debug 17 11 1d02h 13d 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 33 23h22m 14d 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+0x1ec/0x278 lib/vsprintf.c:725
Read of size 1 at addr ffff0000d6ce2611 by task syz.0.17/4536

CPU: 0 PID: 4536 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0xfc mm/kasan/report.c:524
 __asan_report_load1_noabort+0x2c/0x38 mm/kasan/report_generic.c:348
 string_nocheck lib/vsprintf.c:643 [inline]
 string+0x1ec/0x278 lib/vsprintf.c:725
 vsnprintf+0x10ec/0x18d8 lib/vsprintf.c:2805
 va_format lib/vsprintf.c:1685 [inline]
 pointer+0x7ac/0xdd8 lib/vsprintf.c:2436
 vsnprintf+0xcc0/0x18d8 lib/vsprintf.c:2809
 vprintk_store+0x36c/0xb60 kernel/printk/printk.c:2187
 vprintk_emit+0x118/0x2f0 kernel/printk/printk.c:2284
 vprintk_default+0x54/0x80 kernel/printk/printk.c:2318
 vprintk+0x200/0x2a0 kernel/printk/printk_safe.c:45
 _printk+0xe0/0x130 kernel/printk/printk.c:2328
 __dynamic_pr_debug+0x148/0x1e4 lib/dynamic_debug.c:875
 nfc_llcp_wks_sap net/nfc/llcp_core.c:342 [inline]
 nfc_llcp_get_sdp_ssap+0x330/0x394 net/nfc/llcp_core.c:418
 llcp_sock_bind+0x27c/0x540 net/nfc/llcp_sock.c:114
 __sys_bind+0x1f8/0x2a4 net/socket.c:1811
 __do_sys_bind net/socket.c:1822 [inline]
 __se_sys_bind net/socket.c:1820 [inline]
 __arm64_sys_bind+0x7c/0x94 net/socket.c:1820
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Allocated by task 4536:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
 kasan_save_alloc_info+0x24/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0xa0/0xb8 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 __do_kmalloc_node mm/slab_common.c:936 [inline]
 __kmalloc_node_track_caller+0xcc/0x174 mm/slab_common.c:956
 kmemdup+0x5c/0x98 mm/util.c:129
 kmemdup include/linux/fortify-string.h:585 [inline]
 llcp_sock_bind+0x24c/0x540 net/nfc/llcp_sock.c:107
 __sys_bind+0x1f8/0x2a4 net/socket.c:1811
 __do_sys_bind net/socket.c:1822 [inline]
 __se_sys_bind net/socket.c:1820 [inline]
 __arm64_sys_bind+0x7c/0x94 net/socket.c:1820
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the object at ffff0000d6ce2600
 which belongs to the cache kmalloc-128 of size 128
The buggy address is located 17 bytes inside of
 128-byte region [ffff0000d6ce2600, ffff0000d6ce2680)

The buggy address belongs to the physical page:
page:000000003eae1b65 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x116ce2
flags: 0x5ffc00000000200(slab|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000200 0000000000000000 dead000000000122 ffff0000c0002300
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000d6ce2500: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
 ffff0000d6ce2580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff0000d6ce2600: 00 00 01 fc fc fc fc fc fc fc fc fc fc fc fc fc
                         ^
 ffff0000d6ce2680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff0000d6ce2700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (14):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/21 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
2026/09/29 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
2026/09/27 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 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.