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block/vmdk: Report failures in vmdk_read_cid()

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The function vmdk_read_cid() can fail if the read on the underlying
block device fails, or if there's a format error in the VMDK file.
However its API doesn't provide a mechanism to report these errors,
and in some cases we were returning a CID of 0 and in some cases a
CID of 0xffffffff, either of which might potentially be valid values.

Change the function to return 0 on success or a negative errno, and
return the CID via a uint32_t* argument. Update the callsites to
handle and propagate the error appropriately.

This fixes in passing a Coverity-spotted issue (CID 1350038) where
we weren't checking the return value from sscanf().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Peter Maydell 2017-07-09 18:06:14 +01:00 committed by Kevin Wolf
parent 27e4cf1303
commit 9877860e7b
1 changed files with 32 additions and 12 deletions
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44
block/vmdk.c
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@ -242,10 +242,11 @@ static void vmdk_free_last_extent(BlockDriverState *bs)
s->extents = g_renew(VmdkExtent, s->extents, s->num_extents);
}
static uint32_t vmdk_read_cid(BlockDriverState *bs, int parent)
/* Return -ve errno, or 0 on success and write CID into *pcid. */
static int vmdk_read_cid(BlockDriverState *bs, int parent, uint32_t *pcid)
{
char *desc;
uint32_t cid = 0xffffffff;
uint32_t cid;
const char *p_name, *cid_str;
size_t cid_str_size;
BDRVVmdkState *s = bs->opaque;
@ -254,8 +255,7 @@ static uint32_t vmdk_read_cid(BlockDriverState *bs, int parent)
desc = g_malloc0(DESC_SIZE);
ret = bdrv_pread(bs->file, s->desc_offset, desc, DESC_SIZE);
if (ret < 0) {
g_free(desc);
return 0;
goto out;
}
if (parent) {
@ -268,13 +268,21 @@ static uint32_t vmdk_read_cid(BlockDriverState *bs, int parent)
desc[DESC_SIZE - 1] = '\0';
p_name = strstr(desc, cid_str);
if (p_name != NULL) {
p_name += cid_str_size;
sscanf(p_name, "%" SCNx32, &cid);
if (p_name == NULL) {
ret = -EINVAL;
goto out;
}
p_name += cid_str_size;
if (sscanf(p_name, "%" SCNx32, &cid) != 1) {
ret = -EINVAL;
goto out;
}
*pcid = cid;
ret = 0;
out:
g_free(desc);
return cid;
return ret;
}
static int vmdk_write_cid(BlockDriverState *bs, uint32_t cid)
@ -322,7 +330,10 @@ static int vmdk_is_cid_valid(BlockDriverState *bs)
if (!s->cid_checked && bs->backing) {
BlockDriverState *p_bs = bs->backing->bs;
cur_pcid = vmdk_read_cid(p_bs, 0);
if (vmdk_read_cid(p_bs, 0, &cur_pcid) != 0) {
/* read failure: report as not valid */
return 0;
}
if (s->parent_cid != cur_pcid) {
/* CID not valid */
return 0;
@ -975,8 +986,14 @@ static int vmdk_open(BlockDriverState *bs, QDict *options, int flags,
if (ret) {
goto fail;
}
s->cid = vmdk_read_cid(bs, 0);
s->parent_cid = vmdk_read_cid(bs, 1);
ret = vmdk_read_cid(bs, 0, &s->cid);
if (ret) {
goto fail;
}
ret = vmdk_read_cid(bs, 1, &s->parent_cid);
if (ret) {
goto fail;
}
qemu_co_mutex_init(&s->lock);
/* Disable migration when VMDK images are used */
@ -2008,8 +2025,11 @@ static int vmdk_create(const char *filename, QemuOpts *opts, Error **errp)
ret = -EINVAL;
goto exit;
}
parent_cid = vmdk_read_cid(blk_bs(blk), 0);
ret = vmdk_read_cid(blk_bs(blk), 0, &parent_cid);
blk_unref(blk);
if (ret) {
goto exit;
}
snprintf(parent_desc_line, BUF_SIZE,
"parentFileNameHint=\"%s\"", backing_file);
}