In the Linux kernel, the following vulnerability has been resolved:

io_uring/net: fix overflow check in io_recvmsg_mshot_prep()

The "controllen" variable is type size_t (unsigned long).  Casting it
to int could lead to an integer underflow.

The check_add_overflow() function considers the type of the destination
which is type int.  If we add two positive values and the result cannot
fit in an integer then that's counted as an overflow.

However, if we cast "controllen" to an int and it turns negative, then
negative values *can* fit into an int type so there is no overflow.

Good: 100 + (unsigned long)-4 = 96  <-- overflow
 Bad: 100 + (int)-4 = 96 <-- no overflow

I deleted the cast of the sizeof() as well.  That's not a bug but the
cast is unnecessary.

References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2024-35827
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2024/CVE-2024-35827.mbox
https://git.kernel.org/stable/c/868ec868616438df487b9e2baa5a99f8662cc47c
https://git.kernel.org/stable/c/59a534690ecc3af72c6ab121aeac1237a4adae66
https://git.kernel.org/stable/c/0c8c74bb59e7d77554016efc34c2d10376985e5e
https://git.kernel.org/stable/c/b6563ad0d599110bd5cf8f56c47d279c3ed796fe
https://git.kernel.org/stable/c/8ede3db5061bb1fe28e2c9683329aafa89d2b1b4
https://www.cve.org/CVERecord?id=CVE-2024-35827
https://bugzilla.redhat.com/show_bug.cgi?id=2281183