casaroli commented on code in PR #21434:
URL: https://github.com/apache/nuttx/pull/21434#discussion_r4467346911
##########
net/usrsock/usrsock_sendmsg.c:
##########
@@ -160,12 +161,15 @@ static int do_sendto_request(FAR struct usrsock_conn_s
*conn,
for (i = 0; i < msg->msg_iovlen; i++)
{
- req.buflen += msg->msg_iov[i].iov_len;
- }
+ /* The sum of the iov_len values must fit in an ssize_t */
- if (req.buflen > UINT32_MAX)
- {
- req.buflen = UINT32_MAX;
+ if (msg->msg_iov[i].iov_len > SSIZE_MAX - req.buflen)
Review Comment:
On 64-bit `SSIZE_MAX` is far above the range of `req.buflen` (uint32_t), so
two iovecs of 0x80000000 pass this test and `req.buflen` wraps to 0. The wrap
this PR fixes stays on 64-bit arches; UINT32_MAX is the lower bound there,
SSIZE_MAX is the lower bound on 32-bit.
Fix: test `iov_len > MIN(SSIZE_MAX, UINT32_MAX) - req.buflen`, one bound
that holds on both.
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