KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy

Status: upstream: reported C repro on 2026/10/24 11:58
Reported-by: syzbot+0e47336aa0604b3999da@syzkaller.appspotmail.com
First crash: 1d09h, last: 7h18m
▶ ▼ 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 126 3h24m 9h44m 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 8 9h45m 1d01h 0/3 upstream: reported C repro on 2026/10/24 19:51
linux-6.6 KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy 11 syz, C 3 10h11m 1d01h 0/2 upstream: reported C repro on 2026/10/24 20:11

Sample crash report:
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:71 [inline]
BUG: KASAN: null-ptr-deref in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
BUG: KASAN: null-ptr-deref in dm_kcopyd_client_destroy+0xad/0x480 drivers/md/dm-kcopyd.c:970
Read of size 4 at addr 0000000000000174 by task syz.4.31/4545

CPU: 0 PID: 4545 Comm: syz.4.31 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 __kasan_report mm/kasan/report.c:438 [inline]
 kasan_report+0xd5/0x130 mm/kasan/report.c:451
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x235/0x290 mm/kasan/generic.c:189
 instrument_atomic_read include/linux/instrumented.h:71 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
 dm_kcopyd_client_destroy+0xad/0x480 drivers/md/dm-kcopyd.c:970
 __destroy+0x172/0x2f0 drivers/md/dm-cache-target.c:1931
 cache_create drivers/md/dm-cache-target.c:2568 [inline]
 cache_ctr+0x16af/0x2bb0 drivers/md/dm-cache-target.c:2613
 dm_table_add_target+0x5a2/0xba0 drivers/md/dm-table.c:723
 populate_table drivers/md/dm-ioctl.c:1425 [inline]
 table_load+0x2ce/0x760 drivers/md/dm-ioctl.c:1467
 ctl_ioctl drivers/md/dm-ioctl.c:2024 [inline]
 dm_ctl_ioctl+0x947/0xd00 drivers/md/dm-ioctl.c:2046
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 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: 0033:0x7f47624e5559
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:00007f4761b02028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f476276c180 RCX: 00007f47624e5559
RDX: 0000200000000200 RSI: 00000000c138fd09 RDI: 0000000000000003
RBP: 00007f476257cb20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f476276c218 R14: 00007f476276c180 R15: 00007ffe2211bf78
 </TASK>
==================================================================

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/24 15:30 linux-5.15.y 792fbe1537d8 1d9ca40b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/24 13:16 linux-5.15.y 792fbe1537d8 1d9ca40b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/25 14:12 linux-5.15.y 792fbe1537d8 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/25 01:28 linux-5.15.y 792fbe1537d8 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/25 01:28 linux-5.15.y 792fbe1537d8 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/24 11:58 linux-5.15.y 792fbe1537d8 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/24 11:58 linux-5.15.y 792fbe1537d8 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
* Struck through repros no longer work on HEAD.