KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy

Status: upstream: reported C repro on 2026/10/24 20:11
Reported-by: syzbot+78236518a03feaf6e3aa@syzkaller.appspotmail.com
First crash: 1d17h, last: 1d02h
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy dm 11 syz, C error 133 6h13m 1d01h 0/29 upstream: reported C repro on 2026/10/25 11:46
linux-6.1 KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy 11 syz, C 9 10h10m 1d17h 0/3 upstream: reported C repro on 2026/10/24 19:51
linux-5.15 KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy 11 syz, C 7 23h14m 2d01h 0/3 upstream: reported C repro on 2026/10/24 11:58

Sample crash report:
workqueue: Failed to create a rescuer kthread for wq "kcopyd": -EINTR
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:68 [inline]
BUG: KASAN: null-ptr-deref in atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
BUG: KASAN: null-ptr-deref in dm_kcopyd_client_destroy+0xaf/0x490 drivers/md/dm-kcopyd.c:979
Read of size 4 at addr 0000000000000174 by task syz.0.17/6080

CPU: 0 PID: 6080 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x241/0x290 mm/kasan/generic.c:187
 instrument_atomic_read include/linux/instrumented.h:68 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
 dm_kcopyd_client_destroy+0xaf/0x490 drivers/md/dm-kcopyd.c:979
 __destroy+0x172/0x2f0 drivers/md/dm-cache-target.c:1973
 cache_create drivers/md/dm-cache-target.c:2610 [inline]
 cache_ctr+0x1709/0x2c50 drivers/md/dm-cache-target.c:2655
 dm_table_add_target+0x575/0xbc0 drivers/md/dm-table.c:732
 populate_table drivers/md/dm-ioctl.c:1502 [inline]
 table_load+0x2eb/0x7e0 drivers/md/dm-ioctl.c:1544
 ctl_ioctl drivers/md/dm-ioctl.c:2115 [inline]
 dm_ctl_ioctl+0x975/0xd00 drivers/md/dm-ioctl.c:2137
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
 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: 0033:0x7f3399f9f559
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:00007f339af08028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f339a226180 RCX: 00007f3399f9f559
RDX: 0000200000000200 RSI: 00000000c138fd09 RDI: 0000000000000003
RBP: 00007f339a036b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f339a226218 R14: 00007f339a226180 R15: 00007ffc0e094018
 </TASK>
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/24 21:58 linux-6.6.y 0aebf2870d53 1d9ca40b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/25 11:20 linux-6.6.y 0aebf2870d53 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/24 20:10 linux-6.6.y 0aebf2870d53 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
* Struck through repros no longer work on HEAD.