Commit 5a6baf20 authored by Luis Henriques's avatar Luis Henriques Committed by Miklos Szeredi
Browse files

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: default avatar <syzbot+fdebb2dc960aa56c600a@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/all/69917e0d.050a0220.340abe.02e2.GAE@google.com


Fixes: 2396356a ("fuse: add more control over cache invalidation behaviour")
Signed-off-by: default avatarLuis Henriques <luis@igalia.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 8d306cbf

fs/fuse/dir.c

+5 −0
Original line number Diff line number Diff line
@@ -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;

}