- Vulnerability/
- CVE-2022-49052
CVE-2022-49052: mm: fix unexpected zeroed page mapping with zram swap
First published: Wed Feb 26 2025(Updated: )
In the Linux kernel, the following vulnerability has been resolved: mm: fix unexpected zeroed page mapping with zram swap Two processes under CLONE_VM cloning, user process can be corrupted by seeing zeroed page unexpectedly. CPU A CPU B do_swap_page do_swap_page SWP_SYNCHRONOUS_IO path SWP_SYNCHRONOUS_IO path swap_readpage valid data swap_slot_free_notify delete zram entry swap_readpage zeroed(invalid) data pte_lock map the *zero data* to userspace pte_unlock pte_lock if (!pte_same) goto out_nomap; pte_unlock return and next refault will read zeroed data The swap_slot_free_notify is bogus for CLONE_VM case since it doesn't increase the refcount of swap slot at copy_mm so it couldn't catch up whether it's safe or not to discard data from backing device. In the case, only the lock it could rely on to synchronize swap slot freeing is page table lock. Thus, this patch gets rid of the swap_slot_free_notify function. With this patch, CPU A will see correct data. CPU A CPU B do_swap_page do_swap_page SWP_SYNCHRONOUS_IO path SWP_SYNCHRONOUS_IO path swap_readpage original data pte_lock map the original data swap_free swap_range_free bd_disk->fops->swap_slot_free_notify swap_readpage read zeroed data pte_unlock pte_lock if (!pte_same) goto out_nomap; pte_unlock return on next refault will see mapped data by CPU B The concern of the patch would increase memory consumption since it could keep wasted memory with compressed form in zram as well as uncompressed form in address space. However, most of cases of zram uses no readahead and do_swap_page is followed by swap_free so it will free the compressed form from in zram quickly.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel |
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Reference Links
- https://git.kernel.org/stable/c/f86d55cf616199404c05f5b0c5c41b17351baa02
- https://git.kernel.org/stable/c/f098f8b9820fe3f2e41aefc4329dfe8a3859d1c1
- https://git.kernel.org/stable/c/20ed94f8181a25212e7404e44958e234f407624b
- https://git.kernel.org/stable/c/12ba1d38115a101c45d8e0ca3aa1181fd148e57f
- https://git.kernel.org/stable/c/afac4b88699a06c8b9369f9d759a1ec3c254b788
- https://git.kernel.org/stable/c/e914d8f00391520ecc4495dd0ca0124538ab7119
Frequently Asked Questions
What is the severity of CVE-2022-49052?
CVE-2022-49052 has a high severity level as it can lead to process corruption in a multi-threaded environment.
How do I fix CVE-2022-49052?
To fix CVE-2022-49052, you should update your Linux kernel to the latest patched version released by the maintainers.
Which versions of Linux Kernel are affected by CVE-2022-49052?
CVE-2022-49052 affects multiple versions of the Linux kernel prior to the fix being applied; check your version against vendor documentation.
What types of systems are impacted by CVE-2022-49052?
Systems running affected versions of the Linux kernel that utilize zram swap for memory management are impacted by CVE-2022-49052.
What is the potential impact of CVE-2022-49052 on my system?
The potential impact of CVE-2022-49052 includes unexpected behavior in processes resulting from incorrect memory mappings.
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