================================================================== BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:101 [inline] BUG: KASAN: null-ptr-deref in atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:142 [inline] BUG: KASAN: null-ptr-deref in __refcount_add include/linux/refcount.h:193 [inline] BUG: KASAN: null-ptr-deref in __refcount_inc include/linux/refcount.h:250 [inline] BUG: KASAN: null-ptr-deref in refcount_inc include/linux/refcount.h:267 [inline] BUG: KASAN: null-ptr-deref in get_task_struct include/linux/sched/task.h:108 [inline] BUG: KASAN: null-ptr-deref in kthread_stop+0x3a/0x3e0 kernel/kthread.c:640 Write of size 4 at addr 0000000000000020 by task syz.5.17/539 CPU: 0 PID: 539 Comm: syz.5.17 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: __dump_stack+0x21/0x24 lib/dump_stack.c:77 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118 __kasan_report mm/kasan/report.c:439 [inline] kasan_report+0xd8/0x130 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] get_task_struct include/linux/sched/task.h:108 [inline] kthread_stop+0x3a/0x3e0 kernel/kthread.c:640 f2fs_stop_gc_thread+0x65/0xb0 fs/f2fs/gc.c:199 f2fs_ioc_shutdown fs/f2fs/file.c:2415 [inline] __f2fs_ioctl+0x70d6/0xcc90 fs/f2fs/file.c:4384 f2fs_ioctl+0x149/0x240 fs/f2fs/file.c:4469 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:739 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:739 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f9a3a1028f9 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:00007f9a39b49028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f9a3a331080 RCX: 00007f9a3a1028f9 RDX: 0000200000000140 RSI: 000000008004587d RDI: 0000000000000005 RBP: 00007f9a3a1941bc R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f9a3a331080 R15: 00007ffd7a839508 ================================================================== BUG: kernel NULL pointer dereference, address: 0000000000000020 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 1199f9067 P4D 1199f9067 PUD 0 Oops: 0002 [#1] PREEMPT SMP KASAN CPU: 0 PID: 539 Comm: syz.5.17 Tainted: G B syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:arch_atomic_fetch_add arch/x86/include/asm/atomic.h:184 [inline] RIP: 0010:atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:143 [inline] RIP: 0010:__refcount_add include/linux/refcount.h:193 [inline] RIP: 0010:__refcount_inc include/linux/refcount.h:250 [inline] RIP: 0010:refcount_inc include/linux/refcount.h:267 [inline] RIP: 0010:get_task_struct include/linux/sched/task.h:108 [inline] RIP: 0010:kthread_stop+0x40/0x3e0 kernel/kthread.c:640 Code: 00 fc ff df e8 e1 44 22 00 0f 1f 44 00 00 e8 d7 44 22 00 4c 8d 73 20 4c 89 f7 be 04 00 00 00 e8 66 c4 5c 00 41 bf 01 00 00 00 44 0f c1 7b 20 31 ff 44 89 fe e8 60 48 22 00 45 85 ff 0f 84 32 RSP: 0018:ffffc90002ec7898 EFLAGS: 00010246 RAX: ffff88811b0d3b00 RBX: 0000000000000000 RCX: 0000000000000286 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000ffffffff RBP: ffffc90002ec78c0 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffffbfff0dcf448 R12: 1ffff110234b4925 R13: dffffc0000000000 R14: 0000000000000020 R15: 0000000000000001 FS: 00007f9a39b496c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000020 CR3: 0000000119ec8000 CR4: 00000000003506b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: f2fs_stop_gc_thread+0x65/0xb0 fs/f2fs/gc.c:199 f2fs_ioc_shutdown fs/f2fs/file.c:2415 [inline] __f2fs_ioctl+0x70d6/0xcc90 fs/f2fs/file.c:4384 f2fs_ioctl+0x149/0x240 fs/f2fs/file.c:4469 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:739 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:739 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f9a3a1028f9 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:00007f9a39b49028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f9a3a331080 RCX: 00007f9a3a1028f9 RDX: 0000200000000140 RSI: 000000008004587d RDI: 0000000000000005 RBP: 00007f9a3a1941bc R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f9a3a331080 R15: 00007ffd7a839508 Modules linked in: CR2: 0000000000000020 ---[ end trace cda5b726fe5a761a ]--- RIP: 0010:arch_atomic_fetch_add arch/x86/include/asm/atomic.h:184 [inline] RIP: 0010:atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:143 [inline] RIP: 0010:__refcount_add include/linux/refcount.h:193 [inline] RIP: 0010:__refcount_inc include/linux/refcount.h:250 [inline] RIP: 0010:refcount_inc include/linux/refcount.h:267 [inline] RIP: 0010:get_task_struct include/linux/sched/task.h:108 [inline] RIP: 0010:kthread_stop+0x40/0x3e0 kernel/kthread.c:640 Code: 00 fc ff df e8 e1 44 22 00 0f 1f 44 00 00 e8 d7 44 22 00 4c 8d 73 20 4c 89 f7 be 04 00 00 00 e8 66 c4 5c 00 41 bf 01 00 00 00 44 0f c1 7b 20 31 ff 44 89 fe e8 60 48 22 00 45 85 ff 0f 84 32 RSP: 0018:ffffc90002ec7898 EFLAGS: 00010246 RAX: ffff88811b0d3b00 RBX: 0000000000000000 RCX: 0000000000000286 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000ffffffff RBP: ffffc90002ec78c0 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffffbfff0dcf448 R12: 1ffff110234b4925 R13: dffffc0000000000 R14: 0000000000000020 R15: 0000000000000001 FS: 00007f9a39b496c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000020 CR3: 0000000119ec8000 CR4: 00000000003506b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 ---------------- Code disassembly (best guess): 0: 00 fc add %bh,%ah 2: ff lcall (bad) 3: df e8 fucomip %st(0),%st 5: e1 44 loope 0x4b 7: 22 00 and (%rax),%al 9: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) e: e8 d7 44 22 00 call 0x2244ea 13: 4c 8d 73 20 lea 0x20(%rbx),%r14 17: 4c 89 f7 mov %r14,%rdi 1a: be 04 00 00 00 mov $0x4,%esi 1f: e8 66 c4 5c 00 call 0x5cc48a 24: 41 bf 01 00 00 00 mov $0x1,%r15d * 2a: f0 44 0f c1 7b 20 lock xadd %r15d,0x20(%rbx) <-- trapping instruction 30: 31 ff xor %edi,%edi 32: 44 89 fe mov %r15d,%esi 35: e8 60 48 22 00 call 0x22489a 3a: 45 85 ff test %r15d,%r15d 3d: 0f .byte 0xf 3e: 84 32 test %dh,(%rdx)