syzbot


KMSAN: uninit-value in ni_seek_data_or_hole

Status: upstream: reported C repro on 2026/05/26 02:48
Subsystems: ntfs3
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+c2cfe997245202e46f10@syzkaller.appspotmail.com
Fix commit: fs/ntfs3: prevent potential lcn remains uninitialized
Patched on: [ci-upstream-linux-next-kasan-gce-root ci-upstream-rust-kasan-gce], missing on: [ci-qemu-gce-upstream-auto ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb]
First crash: 25d, last: 25d
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
1c6745d6-85df-4642-8c4a-0e3aa6b7d28e assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ KMSAN: uninit-value in ni_seek_data_or_hole 2026/06/02 05:10 2026/06/02 05:10 2026/06/02 05:57 1095583bae1d2729a3b4be301cb6ddc85ced9e38

			
		
Discussions (2)
Title Replies (including bot) Last reply
[PATCH] fs/ntfs3: prevent potential lcn remains uninitialized 2 (2) 2026/06/10 10:43
[syzbot] [ntfs3?] KMSAN: uninit-value in ni_seek_data_or_hole 1 (3) 2026/05/26 07:35
Last patch testing requests (3)
Created Duration User Patch Repo Result
2026/06/06 18:00 1h18m retest repro upstream log
2026/06/06 17:54 1h13m retest repro upstream error
2026/05/26 06:35 42m eadavis@qq.com patch upstream log

Sample crash report:
ntfs3(loop0): Mark volume as dirty due to NTFS errors
ntfs3(loop0): ino=1a, mi_enum_attr
ntfs3(loop0): ino=1a, mi_enum_attr
ntfs3(loop0): Failed to initialize $Extend/$Reparse.
=====================================================
BUG: KMSAN: uninit-value in ni_seek_data_or_hole+0x24f/0x5f0 fs/ntfs3/frecord.c:2862
 ni_seek_data_or_hole+0x24f/0x5f0 fs/ntfs3/frecord.c:2862
 ntfs_llseek+0x22a/0x4a0 fs/ntfs3/file.c:1530
 vfs_llseek fs/read_write.c:391 [inline]
 ksys_lseek fs/read_write.c:404 [inline]
 __do_sys_lseek fs/read_write.c:414 [inline]
 __se_sys_lseek fs/read_write.c:412 [inline]
 __x64_sys_lseek+0x29d/0x460 fs/read_write.c:412
 x64_sys_call+0x3004/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:9
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was stored to memory at:
 ni_seek_data_or_hole+0x248/0x5f0 fs/ntfs3/frecord.c:2862
 ntfs_llseek+0x22a/0x4a0 fs/ntfs3/file.c:1530
 vfs_llseek fs/read_write.c:391 [inline]
 ksys_lseek fs/read_write.c:404 [inline]
 __do_sys_lseek fs/read_write.c:414 [inline]
 __se_sys_lseek fs/read_write.c:412 [inline]
 __x64_sys_lseek+0x29d/0x460 fs/read_write.c:412
 x64_sys_call+0x3004/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:9
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable lcn created at:
 ni_seek_data_or_hole+0x72/0x5f0 fs/ntfs3/frecord.c:2851
 ntfs_llseek+0x22a/0x4a0 fs/ntfs3/file.c:1530

CPU: 0 UID: 0 PID: 5901 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
=====================================================

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/23 12:44 upstream cca95436be15 c69befb3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ni_seek_data_or_hole
2026/05/23 05:45 upstream cca95436be15 c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ni_seek_data_or_hole
2026/05/23 05:45 upstream cca95436be15 c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ni_seek_data_or_hole
2026/05/22 21:33 upstream 6779b50faa56 e16cf9f3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ni_seek_data_or_hole
2026/05/22 21:33 upstream 6779b50faa56 e16cf9f3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-root KMSAN: uninit-value in ni_seek_data_or_hole
2026/05/23 07:01 upstream 45255ea1ca09 c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in ni_seek_data_or_hole
* Struck through repros no longer work on HEAD.