[U-Boot] [PATCH v3 06/13] ext4: scan all directory blocks when looking up an entry

Stefan Brüns
2016-08-28T20:42:31Z

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 Br?ns <stefan.bruens@rwth-aachen.de>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
---
fs/ext4/ext4_common.c | 77 ++++++++++++++++++++++++---------------------------
1 file changed, 36 insertions(+), 41 deletions(-)

v2: unchanged
v3: Added Reviewed-by
use parent_inode instead of g_parent_inode when determining directory size

diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
index 96dc371..eae23b7 100644
--- a/fs/ext4/ext4_common.c
+++ b/fs/ext4/ext4_common.c
@@ -518,64 +518,56 @@ 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;
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);
+
+ block_buffer = zalloc(fs->blksz);
+ if (!block_buffer)
+ goto fail;

- /* read the blocks of parent inode */
- block_buffer = zalloc(fs->blksz);
- if (!block_buffer)
+ /* 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;

+ offset = 0;
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;
- }
+ direntname = (char *)block_buffer + sizeof(struct ext2_dirent);
+ while (le16_to_cpu(dir->direntlen) >= 8) {
+ if (dir->inode && (strlen(dirname) == dir->namelen) &&
+ (strncmp(dirname, direntname, dir->namelen) == 0)) {
+ inodeno = le32_to_cpu(dir->inode);
+ break;
}

- if (fs->blksz - totalbytes == le16_to_cpu(dir->direntlen))
+ offset += le16_to_cpu(dir->direntlen);
+ if (offset >= fs->blksz)
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;
+ dir = (struct ext2_dirent *)(block_buffer + offset);
+ direntname += offset;
}

- free(block_buffer);
- block_buffer = NULL;
-
- if (inodeno > 0)
+ if (inodeno > 0) {
+ free(block_buffer);
return inodeno;
+ }
}

fail:
@@ -827,14 +819,17 @@ 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);
--
2.9.3