linux-kernel - [syzbot] [fuse?] KMSAN: uninit-value in fuse_dentry

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Message-ID: <68d3c631.a70a0220.4f78.001a.GAE@google.com>
Date: Wed, 24 Sep 2025 03:21:37 -0700
From: syzbot <syzbot+743e3f809752d6f7934f@...kaller.appspotmail.com>
To: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	miklos@...redi.hu, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [fuse?] KMSAN: uninit-value in fuse_dentry_revalidate

Hello,

syzbot found the following issue on:

HEAD commit:    cec1e6e5d1ab Merge tag 'sched_ext-for-6.17-rc7-fixes' of g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1404f8e2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1b093ccee5a9e08c
dashboard link: https://syzkaller.appspot.com/bug?extid=743e3f809752d6f7934f
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/da3c94d97543/disk-cec1e6e5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e27bce00cc13/vmlinux-cec1e6e5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f42a4c26986c/bzImage-cec1e6e5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+743e3f809752d6f7934f@...kaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in fuse_dentry_revalidate+0x150/0x13a0 fs/fuse/dir.c:208
 fuse_dentry_revalidate+0x150/0x13a0 fs/fuse/dir.c:208
 d_revalidate fs/namei.c:929 [inline]
 lookup_open fs/namei.c:3637 [inline]
 open_last_lookups fs/namei.c:3807 [inline]
 path_openat+0x13a9/0x6760 fs/namei.c:4043
 do_filp_open+0x280/0x660 fs/namei.c:4073
 do_sys_openat2+0x1bb/0x2f0 fs/open.c:1435
 do_sys_open fs/open.c:1450 [inline]
 __do_compat_sys_openat fs/open.c:1512 [inline]
 __se_compat_sys_openat fs/open.c:1510 [inline]
 __ia32_compat_sys_openat+0x238/0x300 fs/open.c:1510
 ia32_sys_call+0x3210/0x4310 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+0xb0/0x150 arch/x86/entry/syscall_32.c:306
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/syscall_32.c:331
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:369
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4197 [inline]
 slab_alloc_node mm/slub.c:4240 [inline]
 kmem_cache_alloc_lru_noprof+0x822/0xed0 mm/slub.c:4259
 __d_alloc+0x66/0xa60 fs/dcache.c:1690
 d_alloc_parallel+0x98/0x2680 fs/dcache.c:2549
 __lookup_slow+0x138/0x760 fs/namei.c:1793
 lookup_slow+0x6a/0xd0 fs/namei.c:1825
 walk_component+0x444/0x650 fs/namei.c:2129
 lookup_last fs/namei.c:2630 [inline]
 path_lookupat+0x251/0x6b0 fs/namei.c:2654
 filename_lookup+0x2bd/0x800 fs/namei.c:2683
 do_linkat+0x14e/0x1040 fs/namei.c:4904
 __do_sys_link fs/namei.c:4958 [inline]
 __se_sys_link fs/namei.c:4956 [inline]
 __ia32_sys_link+0xd7/0x140 fs/namei.c:4956
 ia32_sys_call+0x3684/0x4310 arch/x86/include/generated/asm/syscalls_32.h:10
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xb0/0x150 arch/x86/entry/syscall_32.c:306
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/syscall_32.c:331
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:369
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

CPU: 0 UID: 0 PID: 8754 Comm: syz.4.604 Not tainted syzkaller #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
=====================================================


---
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