libext2fs: directory iteration mustn't walk off the buffer end

When we're iterating a directory, the loop control code reads the
length of the next directory record, failing to account for the fact
that there must be at least 8 bytes (the minimum size of a directory
entry) left in the buffer to read the next directory record.  Fix the
loop conditional so that we don't read off the end of the buffer.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reported-by: Sami Liedes <sami.liedes@iki.fi>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/lib/ext2fs/dir_iterate.c b/lib/ext2fs/dir_iterate.c
index 589af69..0744ee8 100644 (file)
--- a/lib/ext2fs/dir_iterate.c
+++ b/lib/ext2fs/dir_iterate.c
@@ -202,7 +202,7 @@ int ext2fs_process_dir_block(ext2_filsys fs,
        if (ctx->errcode)
                return BLOCK_ABORT;
 
-       while (offset < fs->blocksize) {
+       while (offset < fs->blocksize - 8) {
                dirent = (struct ext2_dir_entry *) (ctx->buf + offset);
                if (ext2fs_get_rec_len(fs, dirent, &rec_len))
                        return BLOCK_ABORT;