CVE-2025-39793

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

io_uring/memmap: cast nr_pages to size_t before shifting

If the allocated size exceeds UINT_MAX, then its necessary to cast the mr->nr_pages value to size_t to prevent it from overflowing. In practice this isnt much of a concern as the required memory size will have been validated upfront, and accounted to the user. And > 4GB sizes will be necessary to make the lack of a cast a problem, which greatly exceeds normal user locked_vm settings that are generally in the kb to mb range. However, if root is used, then accounting isnt done, and then its possible to hit this issue.

Affected Software

References

• https://git.kernel.org/stable/c/33503c083fda048c77903460ac0429e1e2c0e341
• https://git.kernel.org/stable/c/a69a9b53c54e2d33e2a5b1ea4a9a71fd01c6cf3a
• https://git.kernel.org/stable/c/c6a2706e08b8a1b2d3740161c0977d38e596c1ee