CVE-2024-39497 Information

Description

In the Linux kernel the following vulnerability has been resolved:

drm/shmem-helper: Fix BUG_ON() on mmap(PROT_WRITE MAP_PRIVATE)

Lack of check for copy-on-write (COW) mapping in drm_gem_shmem_mmap allows users to call mmap with PROT_WRITE and MAP_PRIVATE flag causing a kernel panic due to BUG_ON in vmf_insert_pfn_prot: BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(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 PROT_WRITE MAP_PRIVATE fd mmap_offset); ptr[0] = 0;

Reference

https://git.kernel.org/stable/c/1b4a8b89bf6787090b56424d269bf84ba00c3263 https://git.kernel.org/stable/c/03c71c42809ef4b17f5d874cdb2d3bf40e847b86 https://git.kernel.org/stable/c/39bc27bd688066a63e56f7f64ad34fae03fbe3b8