io_uring: fix overflows checks in provide buffers

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: io_uring: fix overflows checks in provide buffers Colin reported before possible overflow and sign extension problems in io_provide_buffers_prep(). As Linus pointed out previous attempt did nothing useful, see d81269fecb8ce ("io_uring: fix provide_buffers sign extension"). Do that with help of check_<op>_overflow helpers. And fix struct io_provide_buf::len type, as it doesn't make much sense to keep it signed.

References

• https://git.kernel.org/stable/c/cbbc13b115b8f18e0a714d89f87fbdc499acfe2d
• https://git.kernel.org/stable/c/51bf90901952aaac564bbdb36b2b503050c53dd9
• https://git.kernel.org/stable/c/84b8c266c4bfe9ed5128e13253c388deb74b1b03
• https://git.kernel.org/stable/c/38134ada0ceea3e848fe993263c0ff6207fd46e7