CVE-2026-31694fuse: reject oversized dirents in page cache

Official description

In the Linux kernel, the following vulnerability has been resolved: fuse: reject oversized dirents in page cache fuse_add_dirent_to_cache() computes a serialized dirent size from the server-controlled namelen field and copies the dirent into a single page-cache page. The existing logic only checks whether the dirent fits in the remaining space of the current page and advances to a fresh page if not. It never checks whether the dirent itself exceeds PAGE_SIZE. As a result, a malicious FUSE server can return a dirent with namelen=4095, producing a serialized record size of 4120 bytes. On 4 KiB page systems this causes memcpy() to overflow the cache page by 24 bytes into the following kernel page. Reject dirents that cannot fit in a single page before copying them into the readdir cache.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/7de93abfaae1b2dc94da8a07a36421bd073f1d8f
• https://git.kernel.org/stable/c/474ce83c96a55f2eeb14dee2be375eeadfdacdf5
• https://git.kernel.org/stable/c/51a8de6c50bf947c8f534cd73da4c8f0a13e7bed
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html