ext4: Scan all directory blocks when looking up an entry

Scanning only the direct blocks of the directory file may falsely report
an existing file as nonexisting, and worse can also lead to creation
of a duplicate entry on file creation.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>

fs/ext4/ext4_common.c

@@ -525,64 +525,57 @@ static int search_dir(struct ext2_inode *parent_inode, char *dirname)
 {
 	int status;
 	int inodeno = 0;
-	int totalbytes;
-	int templength;
-	int direct_blk_idx;
+	int offset;
+	int blk_idx;
 	long int blknr;
-	char *ptr = NULL;
-	unsigned char *block_buffer = NULL;
+	char *block_buffer = NULL;
 	struct ext2_dirent *dir = NULL;
 	struct ext_filesystem *fs = get_fs();
+	uint32_t directory_blocks;
+	char *direntname;
 
-	/* read the block no allocated to a file */
-	for (direct_blk_idx = 0; direct_blk_idx < INDIRECT_BLOCKS;
-		direct_blk_idx++) {
-		blknr = read_allocated_block(parent_inode, direct_blk_idx);
-		if (blknr == 0)
-			goto fail;
+	directory_blocks = le32_to_cpu(parent_inode->size) >>
+		LOG2_BLOCK_SIZE(ext4fs_root);
 
-		/* read the blocks of parent inode */
-		block_buffer = zalloc(fs->blksz);
-		if (!block_buffer)
+	block_buffer = zalloc(fs->blksz);
+	if (!block_buffer)
+		goto fail;
+
+	/* get the block no allocated to a file */
+	for (blk_idx = 0; blk_idx < directory_blocks; blk_idx++) {
+		blknr = read_allocated_block(parent_inode, blk_idx);
+		if (blknr == 0)
 			goto fail;
 
+		/* read the directory block */
 		status = ext4fs_devread((lbaint_t)blknr * fs->sect_perblk,
 					0, fs->blksz, (char *)block_buffer);
 		if (status == 0)
 			goto fail;
 
-		dir = (struct ext2_dirent *)block_buffer;
-		ptr = (char *)dir;
-		totalbytes = 0;
-		while (le16_to_cpu(dir->direntlen) >= 0) {
-			/*
-			 * blocksize-totalbytes because last directory
-			 * length i.e.,*dir->direntlen is free availble
-			 * space in the block that means
-			 * it is a last entry of directory entry
-			 */
-			if (dir->inode && (strlen(dirname) == dir->namelen)) {
-				if (strncmp(dirname, ptr + sizeof(struct ext2_dirent), dir->namelen) == 0) {
-					inodeno = le32_to_cpu(dir->inode);
-					break;
-				}
-			}
+		offset = 0;
+		do {
+			dir = (struct ext2_dirent *)(block_buffer + offset);
+			direntname = (char*)(dir) + sizeof(struct ext2_dirent);
 
-			if (fs->blksz - totalbytes == le16_to_cpu(dir->direntlen))
+			int direntlen = le16_to_cpu(dir->direntlen);
+			if (direntlen < sizeof(struct ext2_dirent))
 				break;
 
-			/* traversing the each directory entry */
-			templength = le16_to_cpu(dir->direntlen);
-			totalbytes = totalbytes + templength;
-			dir = (struct ext2_dirent *)((char *)dir + templength);
-			ptr = (char *)dir;
-		}
+			if (dir->inode && (strlen(dirname) == dir->namelen) &&
+			    (strncmp(dirname, direntname, dir->namelen) == 0)) {
+				inodeno = le32_to_cpu(dir->inode);
+				break;
+			}
+
+			offset += direntlen;
 
-		free(block_buffer);
-		block_buffer = NULL;
+		} while (offset < fs->blksz);
 
-		if (inodeno > 0)
+		if (inodeno > 0) {
+			free(block_buffer);
 			return inodeno;
+		}
 	}
 
 fail:
@@ -834,14 +827,17 @@ fail:
 
 int ext4fs_filename_unlink(char *filename)
 {
-	short direct_blk_idx = 0;
+	int blk_idx;
 	long int blknr = -1;
 	int inodeno = -1;
+	uint32_t directory_blocks;
+
+	directory_blocks = le32_to_cpu(g_parent_inode->size) >>
+		LOG2_BLOCK_SIZE(ext4fs_root);
 
 	/* read the block no allocated to a file */
-	for (direct_blk_idx = 0; direct_blk_idx < INDIRECT_BLOCKS;
-		direct_blk_idx++) {
-		blknr = read_allocated_block(g_parent_inode, direct_blk_idx);
+	for (blk_idx = 0; blk_idx < directory_blocks; blk_idx++) {
+		blknr = read_allocated_block(g_parent_inode, blk_idx);
 		if (blknr == 0)
 			break;
 		inodeno = unlink_filename(filename, blknr);