eCryptfs: Remove buggy and unnecessary write in file name decode routine

Dmitry Chernenkov used KASAN to discover that eCryptfs writes past the
end of the allocated buffer during encrypted filename decoding. This
fix corrects the issue by getting rid of the unnecessary 0 write when
the current bit offset is 2.

Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Reported-by: Dmitry Chernenkov <dmitryc@google.com>
Suggested-by: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org # v2.6.29+: 51ca58d eCryptfs: Filename Encryption: Encoding and encryption functions
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index 2f6735dbf1a9..31b148f3e772 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -1917,7 +1917,6 @@ ecryptfs_decode_from_filename(unsigned char *dst, size_t *dst_size,
                         break;
                 case 2:
                         dst[dst_byte_offset++] |= (src_byte);
-                        dst[dst_byte_offset] = 0;
                         current_bit_offset = 0;
                         break;
                 }