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

Stefan Brüns
2016-10-09T18:15:27Z

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;
--
2.10.0