[U-Boot] [PATCH 2/3] ext4: Fix handling of direntlen in unlink_filename

Lukasz Majewski
2016-10-14T10:29:54Z

Hi Stefan,

> The direntlen checks were quite bogus, i.e. the loop termination used
> "len + offset == blocksize" (exact match only), and checked for a
> direntlen less than 0. The latter can never happen as the len is
> unsigned, this has been reported by Coverity, CID 153384.
>
> Use the same code as in search_dir for directory traversal. This code
> has the correct checks for direntlen >= sizeof(struct dirent), and
> offset < blocksize.
>
> Signed-off-by: Stefan Br?ns <stefan.bruens@rwth-aachen.de>
> ---
> fs/ext4/ext4_common.c | 45
> +++++++++++++++++---------------------------- 1 file changed, 17
> insertions(+), 28 deletions(-)
>
> diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
> index 699a640..11be0b7 100644
> --- a/fs/ext4/ext4_common.c
> +++ b/fs/ext4/ext4_common.c
> @@ -854,16 +854,15 @@ fail:
>
> static int unlink_filename(char *filename, unsigned int blknr)
> {
> - int templength = 0;
> - int status, inodeno;
> - int found = 0;
> + int status;
> + int inodeno = 0;
> int offset;
> char *block_buffer = NULL;
> struct ext2_dirent *dir = NULL;
> - struct ext2_dirent *previous_dir = NULL;
> - char *ptr = NULL;
> + struct ext2_dirent *previous_dir;
> struct ext_filesystem *fs = get_fs();
> int ret = -1;
> + char *direntname;
>
> block_buffer = zalloc(fs->blksz);
> if (!block_buffer)
> @@ -877,20 +876,18 @@ static int unlink_filename(char *filename,
> unsigned int blknr)
> if (ext4fs_log_journal(block_buffer, blknr))
> goto fail;
> - dir = (struct ext2_dirent *)block_buffer;
> - ptr = (char *)dir;
> offset = 0;
> - while (le16_to_cpu(dir->direntlen) >= 0) {
> - /*
> - * blocksize-offset 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
> - */
> + do {
> + previous_dir = dir;
> + dir = (struct ext2_dirent *)(block_buffer + offset);
> + direntname = (char *)(dir) + sizeof(struct
> ext2_dirent); +
> + int direntlen = le16_to_cpu(dir->direntlen);
> + if (direntlen < sizeof(struct ext2_dirent))
> + break;
> +
> if (dir->inode && (strlen(filename) == dir->namelen)
> &&
> - (strncmp(ptr + sizeof(struct ext2_dirent),
> - filename, dir->namelen) == 0)) {
> - printf("file found, deleting\n");
> + (strncmp(direntname, filename, dir->namelen) ==
> 0)) { inodeno = le32_to_cpu(dir->inode);
> if (previous_dir) {
> uint16_t new_len;
> @@ -900,23 +897,15 @@ static int unlink_filename(char *filename,
> unsigned int blknr) } else {
> dir->inode = 0;
> }
> - found = 1;
> break;
> }
>
> - if (fs->blksz - offset ==
> le16_to_cpu(dir->direntlen))
> - break;
> + offset += direntlen;
>
> - /* traversing the each directory entry */
> - templength = le16_to_cpu(dir->direntlen);
> - offset = offset + templength;
> - previous_dir = dir;
> - dir = (struct ext2_dirent *)((char *)dir +
> templength);
> - ptr = (char *)dir;
> - }
> + } while (offset < fs->blksz);
>
> + if (inodeno > 0) {
>
> - if (found == 1) {
> if (ext4fs_put_metadata(block_buffer, blknr))
> goto fail;
> ret = inodeno;

Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>

--
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group