KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy

Status: upstream: reported C repro on 2026/10/24 19:51
Reported-by: syzbot+bfdb227e582d73eb8907@syzkaller.appspotmail.com
First crash: 22h18m, last: 6h22m
▶ ▼ 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 now 6h22m 0/29 upstream: reported C repro on 2026/10/25 11:46
linux-5.15 KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy 11 syz, C 7 3h56m 1d06h 0/3 upstream: reported C repro on 2026/10/24 11:58
linux-6.6 KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy 11 syz, C 3 6h48m 21h57m 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:72 [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+0xab/0x480 drivers/md/dm-kcopyd.c:972
Read of size 4 at addr 0000000000000174 by task syz.1.56/4845

CPU: 0 PID: 4845 Comm: syz.1.56 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 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:72 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
 dm_kcopyd_client_destroy+0xab/0x480 drivers/md/dm-kcopyd.c:972
 __destroy+0x172/0x2f0 drivers/md/dm-cache-target.c:1955
 cache_create drivers/md/dm-cache-target.c:2592 [inline]
 cache_ctr+0x1701/0x2c70 drivers/md/dm-cache-target.c:2637
 dm_table_add_target+0x571/0xbc0 drivers/md/dm-table.c:733
 populate_table drivers/md/dm-ioctl.c:1440 [inline]
 table_load+0x2ce/0x760 drivers/md/dm-ioctl.c:1482
 ctl_ioctl drivers/md/dm-ioctl.c:2055 [inline]
 dm_ctl_ioctl+0xa9c/0xec0 drivers/md/dm-ioctl.c:2077
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa033d9f559
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:00007fa034cdb028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa034026090 RCX: 00007fa033d9f559
RDX: 0000200000000200 RSI: 00000000c138fd09 RDI: 0000000000000003
RBP: 00007fa033e36b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa034026128 R14: 00007fa034026090 R15: 00007fff0c20b2d8
 </TASK>
==================================================================

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/24 21:13 linux-6.1.y 79807e970724 1d9ca40b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/25 11:45 linux-6.1.y 79807e970724 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/24 20:03 linux-6.1.y 79807e970724 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/24 20:00 linux-6.1.y 79807e970724 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/24 19:56 linux-6.1.y 79807e970724 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/24 19:50 linux-6.1.y 79807e970724 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/25 10:49 linux-6.1.y 79807e970724 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
2026/10/25 04:02 linux-6.1.y 79807e970724 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: null-ptr-deref Read in dm_kcopyd_client_destroy
* Struck through repros no longer work on HEAD.