syzbot


KMSAN: uninit-value in ovl_fill_real

Status: upstream: reported on 2026/01/22 13:09
Subsystems: overlayfs
[Documentation on labels]
Reported-by: syzbot+d130f98b2c265fae5297@syzkaller.appspotmail.com
First crash: 8d10h, last: 8d10h
Discussions (2)
Title Replies (including bot) Last reply
[PATCH] fscrypt: Fix uninit-value in ovl_fill_real 4 (4) 2026/01/26 06:33
[syzbot] [overlayfs?] KMSAN: uninit-value in ovl_fill_real 0 (1) 2026/01/22 13:09

Sample crash report:
EXT4-fs: Quota format mount options ignored when QUOTA feature is enabled
EXT4-fs (loop1): Test dummy encryption mode enabled
EXT4-fs (loop1): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
=====================================================
BUG: KMSAN: uninit-value in ovl_fill_real+0x1df/0x920 fs/overlayfs/readdir.c:758
 ovl_fill_real+0x1df/0x920 fs/overlayfs/readdir.c:758
 dir_emit include/linux/fs.h:3527 [inline]
 ext4_readdir+0x320e/0x6f30 fs/ext4/dir.c:304
 iterate_dir+0x452/0x620 fs/readdir.c:108
 ovl_iterate_real fs/overlayfs/readdir.c:829 [inline]
 ovl_iterate+0x1e84/0x47d0 fs/overlayfs/readdir.c:909
 wrap_directory_iterator+0xda/0x180 fs/readdir.c:65
 shared_ovl_iterate+0x3d/0x50 fs/overlayfs/readdir.c:1065
 iterate_dir+0x452/0x620 fs/readdir.c:108
 __do_sys_getdents64 fs/readdir.c:410 [inline]
 __se_sys_getdents64+0x17e/0x550 fs/readdir.c:396
 __ia32_sys_getdents64+0x96/0xe0 fs/readdir.c:396
 ia32_sys_call+0x353e/0x4340 arch/x86/include/generated/asm/syscalls_32.h:221
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0x154/0x320 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/syscall_32.c:332
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:370
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4960 [inline]
 slab_alloc_node mm/slub.c:5263 [inline]
 __do_kmalloc_node mm/slub.c:5656 [inline]
 __kmalloc_noprof+0xaf2/0x1c20 mm/slub.c:5669
 kmalloc_noprof include/linux/slab.h:961 [inline]
 fscrypt_fname_alloc_buffer+0x52/0x110 fs/crypto/fname.c:223
 ext4_readdir+0xaf6/0x6f30 fs/ext4/dir.c:169
 iterate_dir+0x452/0x620 fs/readdir.c:108
 ovl_iterate_real fs/overlayfs/readdir.c:829 [inline]
 ovl_iterate+0x1e84/0x47d0 fs/overlayfs/readdir.c:909
 wrap_directory_iterator+0xda/0x180 fs/readdir.c:65
 shared_ovl_iterate+0x3d/0x50 fs/overlayfs/readdir.c:1065
 iterate_dir+0x452/0x620 fs/readdir.c:108
 __do_sys_getdents64 fs/readdir.c:410 [inline]
 __se_sys_getdents64+0x17e/0x550 fs/readdir.c:396
 __ia32_sys_getdents64+0x96/0xe0 fs/readdir.c:396
 ia32_sys_call+0x353e/0x4340 arch/x86/include/generated/asm/syscalls_32.h:221
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0x154/0x320 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/syscall_32.c:332
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:370
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

CPU: 1 UID: 0 PID: 30053 Comm: syz.1.3910 Tainted: G             L      syzkaller #0 PREEMPT(none) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
=====================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/18 13:04 upstream d12453c7e281 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in ovl_fill_real
* Struck through repros no longer work on HEAD.