CVE-2024-42233 Information

Description

In the Linux kernel the following vulnerability has been resolved:

filemap: replace pte_offset_map() with pte_offset_map_nolock()

The vmf->ptl in filemap_fault_recheck_pte_none() is still set from handle_pte_fault(). But at the same time we did a pte_unmap(vmf->pte). After a pte_unmap(vmf->pte) unmap and rcu_read_unlock() the page table may be racily changed and vmf->ptl maybe fails to protect the actual page table. Fix this by replacing pte_offset_map() with pte_offset_map_nolock().

As David said the PTL pointer might be stale so if we continue to use it infilemap_fault_recheck_pte_none() it might trigger UAF. Also if the PTL fails the issue fixed by commit 58f327f2ce80 (ilemap: avoid unnecessary major faults in filemap_fault()) might reappear.

Reference

https://git.kernel.org/stable/c/6a6c2aec1a89506595801b4cf7e8eef035f33748 https://git.kernel.org/stable/c/24be02a42181f0707be0498045c4c4b13273b16d