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ext4: Fix handling of direntlen in unlink_filename

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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 Brüns <stefan.bruens@rwth-aachen.de>
Reported-by: Coverity (CID: 153383, 153384)
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
This commit is contained in:
Stefan Brüns 2016-10-09 20:15:27 +02:00 committed by Tom Rini
parent 15bf8c4f93
commit d1bdf22461
1 changed files with 17 additions and 28 deletions
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45
fs/ext4/ext4_common.c
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@ -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;