CVE-2024-39497

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

drm/shmem-helper: Fix BUGON() on mmap(PROTWRITE, MAP_PRIVATE)

Lack of check for copy-on-write (COW) mapping in drmgemshmemmmap allows users to call mmap with PROTWRITE and MAPPRIVATE flag causing a kernel panic due to BUGON in vmfinsertpfnprot: BUGON((vma->vmflags & VMPFNMAP) && iscowmapping(vma->vm_flags));

Return -EINVAL early if COW mapping is detected.

This bug affects all drm drivers using default shmem helpers. It can be reproduced by this simple example: void *ptr = mmap(0, size, PROTWRITE, MAPPRIVATE, fd, mmap_offset); ptr[0] = 0;