KASAN: use-after-free Write in config_item_get

Status: upstream: reported C repro on 2026/07/26 20:05
Reported-by: syzbot+54306154561c48ff71a9@syzkaller.appspotmail.com
First crash: 15d, last: 13d
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 KASAN: use-after-free Write in config_item_get origin:upstream 22 syz, C 1 16d 16d 0/3 upstream: reported C repro on 2026/07/25 19:17
android-5-15 KASAN: use-after-free Write in config_item_get 22 syz, C 5 11d 13d 0/2 upstream: reported C repro on 2026/07/28 10:17
linux-6.6 KASAN: slab-use-after-free Write in config_item_get 22 syz, C 1 1d21h 1d21h 0/2 upstream: reported C repro on 2026/08/09 00:32
upstream KASAN: slab-use-after-free Write in config_item_get fs prio:normal 22 syz, C error 8 8d07h 11d 0/29 upstream: reported C repro on 2026/07/30 00:19
android-6-12 KASAN: slab-use-after-free Write in config_item_get 22 syz 2 11d 11d 0/1 premoderation: reported syz repro on 2026/07/30 06:38

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:142 [inline]
BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: use-after-free in kref_get include/linux/kref.h:45 [inline]
BUG: KASAN: use-after-free in config_item_get+0x27/0x90 fs/configfs/item.c:106
Write of size 4 at addr ffff888112a5e41c by task syz.3.4939/5367

CPU: 1 PID: 5367 Comm: syz.3.4939 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0x100/0x140 mm/kasan/report.c:452
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x249/0x2a0 mm/kasan/generic.c:189
 __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:142 [inline]
 __refcount_add include/linux/refcount.h:193 [inline]
 __refcount_inc include/linux/refcount.h:250 [inline]
 refcount_inc include/linux/refcount.h:267 [inline]
 kref_get include/linux/kref.h:45 [inline]
 config_item_get+0x27/0x90 fs/configfs/item.c:106
 configfs_get_config_item fs/configfs/configfs_internal.h:128 [inline]
 get_target fs/configfs/symlink.c:127 [inline]
 configfs_symlink+0x44f/0x1320 fs/configfs/symlink.c:192
 vfs_symlink+0x339/0x4c0 fs/namei.c:4107
 do_symlinkat+0x10e/0x3d0 fs/namei.c:4134
 __do_sys_symlinkat fs/namei.c:4148 [inline]
 __se_sys_symlinkat fs/namei.c:4145 [inline]
 __x64_sys_symlinkat+0x7b/0x90 fs/namei.c:4145
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f435fd25e99
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:00007ffcae75c908 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f435ffadfa0 RCX: 00007f435fd25e99
RDX: 0000200000000340 RSI: ffffffffffffff9c RDI: 0000200000000300

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/28 21:14 android13-5.10-lts 50b3a256e550 edc8a875 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in config_item_get
2026/07/27 22:33 android13-5.10-lts 50b3a256e550 aae9036b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in config_item_get
2026/07/26 23:33 android13-5.10-lts 50b3a256e550 492bab15 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in config_item_get
2026/07/26 20:04 android13-5.10-lts 50b3a256e550 492bab15 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Write in config_item_get
* Struck through repros no longer work on HEAD.