CVE-2024-49872

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

mm/gup: fix memfdpinfolios alloc race panic

If memfdpinfolios tries to create a hugetlb page, but someone else already did, then folio gets the value -EEXIST here:

    folio = memfd_alloc_folio(memfd, start_idx);
    if (IS_ERR(folio)) {
            ret = PTR_ERR(folio);
            if (ret != -EEXIST)
                    goto err;

then on the next trip through the "while start_idx" loop we panic here:

    if (folio) {
            folio_put(folio);

To fix, set the folio to NULL on error.