From: Luis Henriques Date: Mon, 16 Feb 2026 14:48:30 +0000 (+0000) Subject: fuse: fix uninit-value in fuse_dentry_revalidate() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5a6baf204610589f8a5b5a1cd69d1fe661d9d3cd;p=thirdparty%2Fkernel%2Flinux.git fuse: fix uninit-value in fuse_dentry_revalidate() fuse_dentry_revalidate() may be called with a dentry that didn't had ->d_time initialised. The issue was found with KMSAN, where lookup_open() calls __d_alloc(), followed by d_revalidate(), as shown below: ===================================================== BUG: KMSAN: uninit-value in fuse_dentry_revalidate+0x150/0x13d0 fs/fuse/dir.c:394 fuse_dentry_revalidate+0x150/0x13d0 fs/fuse/dir.c:394 d_revalidate fs/namei.c:1030 [inline] lookup_open fs/namei.c:4405 [inline] open_last_lookups fs/namei.c:4583 [inline] path_openat+0x1614/0x64c0 fs/namei.c:4827 do_file_open+0x2aa/0x680 fs/namei.c:4859 [...] Uninit was created at: slab_post_alloc_hook mm/slub.c:4466 [inline] slab_alloc_node mm/slub.c:4788 [inline] kmem_cache_alloc_lru_noprof+0x382/0x1280 mm/slub.c:4807 __d_alloc+0x55/0xa00 fs/dcache.c:1740 d_alloc_parallel+0x99/0x2740 fs/dcache.c:2604 lookup_open fs/namei.c:4398 [inline] open_last_lookups fs/namei.c:4583 [inline] path_openat+0x135f/0x64c0 fs/namei.c:4827 do_file_open+0x2aa/0x680 fs/namei.c:4859 [...] ===================================================== Reported-by: syzbot+fdebb2dc960aa56c600a@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/69917e0d.050a0220.340abe.02e2.GAE@google.com Fixes: 2396356a945b ("fuse: add more control over cache invalidation behaviour") Signed-off-by: Luis Henriques Signed-off-by: Miklos Szeredi --- diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 70d3e631266e1..b658b6baf72fe 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -480,6 +480,11 @@ static int fuse_dentry_init(struct dentry *dentry) fd->dentry = dentry; RB_CLEAR_NODE(&fd->node); dentry->d_fsdata = fd; + /* + * Initialising d_time (epoch) to '0' ensures the dentry is invalid + * if compared to fc->epoch, which is initialized to '1'. + */ + dentry->d_time = 0; return 0; }