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Subject[PATCH 4.14 044/173] ubifs: dont trigger assertion on invalid no-key filename
Date
From: Eric Biggers <ebiggers@google.com>

[ Upstream commit f0d07a98a070bb5e443df19c3aa55693cbca9341 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ubifs/dir.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 4e6e32c0c08a4..358abc26dbc0b 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -253,6 +253,8 @@ static struct dentry *ubifs_lookup(struct inode *dir, struct dentry *dentry,
if (nm.hash) {
ubifs_assert(fname_len(&nm) == 0);
ubifs_assert(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 {
--
2.20.1


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