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libvhost-user: check for NULL when allocating a virtqueue element 

Check the return value for malloc(), avoiding a NULL pointer
dereference, and propagate error in function callers.

Found with GCC 13 and -fanalyzer:

../subprojects/libvhost-user/libvhost-user.c: In function ‘virtqueue_alloc_element’:
../subprojects/libvhost-user/libvhost-user.c:2556:19: error: dereference of possibly-NULL ‘elem’ [CWE-690] [-Werror=analyzer-possible-null-dereference]
 2556 |     elem->out_num = out_num;
      |     ~~~~~~~~~~~~~~^~~~~~~~~
  ‘virtqueue_alloc_element’: event 1
    |
    | 2554 |     assert(sz >= sizeof(VuVirtqElement));
    |      |     ^~~~~~
    |      |     |
    |      |     (1) following ‘true’ branch (when ‘sz > 31’)...
    |
  ‘virtqueue_alloc_element’: events 2-4
    |
    | 2555 |     elem = malloc(out_sg_end);
    |      |     ^~~~   ~~~~~~~~~~~~~~~~~~
    |      |     |      |
    |      |     |      (3) this call could return NULL
    |      |     (2) ...to here
    | 2556 |     elem->out_num = out_num;
    |      |     ~~~~~~~~~~~~~~~~~~~~~~~
    |      |                   |
    |      |                   (4) ‘elem’ could be NULL: unchecked value from (3)
    |

Signed-off-by: Carlos López <clopez@suse.de>
Message-Id: <20230210112514.16858-1-clopez@suse.de>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 9c1916057a)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
This commit is contained in:
Carlos López 2023-02-10 12:25:15 +01:00 committed by Michael Tokarev
parent a7485cdca7
commit 6cf13d9d01
1 changed files with 7 additions and 0 deletions
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7
subprojects/libvhost-user/libvhost-user.c
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@ -2547,6 +2547,10 @@ virtqueue_alloc_element(size_t sz,
assert(sz >= sizeof(VuVirtqElement));
elem = malloc(out_sg_end);
if (!elem) {
DPRINT("%s: failed to malloc virtqueue element\n", __func__);
return NULL;
}
elem->out_num = out_num;
elem->in_num = in_num;
elem->in_sg = (void *)elem + in_sg_ofs;
@ -2633,6 +2637,9 @@ vu_queue_map_desc(VuDev *dev, VuVirtq *vq, unsigned int idx, size_t sz)
/* Now copy what we have collected and mapped */
elem = virtqueue_alloc_element(sz, out_num, in_num);
if (!elem) {
return NULL;
}
elem->index = idx;
for (i = 0; i < out_num; i++) {
elem->out_sg[i] = iov[i];