syzbot


KMSAN: uninit-value in alloc_fd

Status: moderation: reported on 2026/05/29 22:35
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+69acc0e826171a4222c9@syzkaller.appspotmail.com
First crash: 4d12h, last: 4d12h

Sample crash report:
=====================================================
BUG: KMSAN: uninit-value in alloc_fd+0x31b/0xc60 fs/file.c:584
 alloc_fd+0x31b/0xc60 fs/file.c:584
 __get_unused_fd_flags fs/file.c:617 [inline]
 get_unused_fd_flags+0x6f/0xa0 fs/file.c:622
 do_sys_openat2+0xf2/0x370 fs/open.c:1364
 do_sys_open fs/open.c:1370 [inline]
 __do_compat_sys_openat fs/open.c:1432 [inline]
 __se_compat_sys_openat fs/open.c:1430 [inline]
 __ia32_compat_sys_openat+0x238/0x300 fs/open.c:1430
 ia32_sys_call+0x330b/0x4360 arch/x86/include/generated/asm/syscalls_32.h:296
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0x180/0x460 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x37/0x80 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:4577 [inline]
 slab_alloc_node mm/slub.c:4899 [inline]
 kmem_cache_alloc_noprof+0x373/0x1250 mm/slub.c:4906
 dup_fd+0x66/0x1160 fs/file.c:390
 copy_files+0x10c/0x250 kernel/fork.c:1639
 copy_process+0x3018/0x6ad0 kernel/fork.c:2252
 kernel_clone+0x4d4/0x1190 kernel/fork.c:2721
 __do_compat_sys_ia32_clone arch/x86/kernel/sys_ia32.c:255 [inline]
 __se_compat_sys_ia32_clone arch/x86/kernel/sys_ia32.c:241 [inline]
 __ia32_compat_sys_ia32_clone+0x251/0x360 arch/x86/kernel/sys_ia32.c:241
 ia32_sys_call+0x1c6d/0x4360 arch/x86/include/generated/asm/syscalls_32.h:121
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0x180/0x460 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x37/0x80 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: 6128 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
=====================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/25 22:29 upstream e7ae89a0c97c c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kmsan-gce-386-root KMSAN: uninit-value in alloc_fd
* Struck through repros no longer work on HEAD.