linux-kernel - [PATCH v5 4/6] ubifs: don't trigger assertion on invalid no-key filename

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Message-Id: <20200120223201.241390-5-ebiggers@kernel.org>
Date:   Mon, 20 Jan 2020 14:31:59 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     linux-fscrypt@...r.kernel.org
Cc:     Daniel Rosenberg <drosen@...gle.com>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        linux-mtd@...ts.infradead.org, Richard Weinberger <richard@....at>
Subject: [PATCH v5 4/6] ubifs: don't trigger assertion on invalid no-key filename

From: Eric Biggers <ebiggers@...gle.com>

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@...r.kernel.org> # v4.10+
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 fs/ubifs/dir.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 636c3222c2308..5f937226976a6 100644
--- 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 {
-- 
2.25.0