Linux Kernel up to 6.9.9 pte_offset_map use after free

Summaryinfo

A vulnerability identified as critical has been detected in Linux Kernel up to 6.9.9. Affected is the function pte_offset_map. This manipulation causes use after free. This vulnerability is tracked as CVE-2024-42233. No exploit exists. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.9.9. It has been declared as critical. Affected by this vulnerability is the function pte_offset_map. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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 ("filemap: avoid unnecessary major faults in filemap_fault()") might reappear.

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2024-42233 since 07/30/2024. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/09/2024).

Upgrading to version 6.9.10 eliminates this vulnerability. Applying the patch 6a6c2aec1a89/24be02a42181 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.9.0
• 6.9.1
• 6.9.2
• 6.9.3
• 6.9.4
• 6.9.5
• 6.9.6
• 6.9.7
• 6.9.8
• 6.9.9

License

• open-source

Website

• Vendor: https://www.kernel.org/

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