ubifs: don't trigger assertion on invalid no-key filename

If userspace provides an invalid fscrypt no-key filename which encodes a
hash value with any of the UBIFS node type bits set (i.e. the high 3
bits), gracefully report ENOENT rather than triggering ubifs_assert().

Test case with kvm-xfstests shell:

    . fs/ubifs/config
    . ~/xfstests/common/encrypt
    dev=$(__blkdev_to_ubi_volume /dev/vdc)
    ubiupdatevol $dev -t
    mount $dev /mnt -t ubifs
    mkdir /mnt/edir
    xfs_io -c set_encpolicy /mnt/edir
    rm /mnt/edir/_,,,,,DAAAAAAAAAAAAAAAAAAAAAAAAAA

With the bug, the following assertion fails on the 'rm' command:

    [   19.066048] UBIFS error (ubi0:0 pid 379): ubifs_assert_failed: UBIFS assert failed: !(hash & ~UBIFS_S_KEY_HASH_MASK), in fs/ubifs/key.h:170

Fixes: f4f61d2cc6d8 ("ubifs: Implement encrypted filenames")
Cc: <stable@vger.kernel.org> # v4.10+
Link: https://lore.kernel.org/r/20200120223201.241390-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 636c3222c2308bc77c24bf2099ba26c3b6e5e676..5f937226976a621c55c497155db5f5b0a0072ae5 100644 (file)
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -228,6 +228,8 @@ static struct dentry *ubifs_lookup(struct inode *dir, struct dentry *dentry,
        if (nm.hash) {
                ubifs_assert(c, fname_len(&nm) == 0);
                ubifs_assert(c, fname_name(&nm) == NULL);
+               if (nm.hash & ~UBIFS_S_KEY_HASH_MASK)
+                       goto done; /* ENOENT */
                dent_key_init_hash(c, &key, dir->i_ino, nm.hash);
                err = ubifs_tnc_lookup_dh(c, &key, dent, nm.minor_hash);
        } else {