# CVE-2022-49052: linux: In the Linux kernel, the following vulnerability has been resolved:  mm: fix unexpected zeroed page mapping with zram...

CVE-2022-49052 is fixed in linux on 1 platform, first by DEBIAN-CVE-2022-49052, released February 26, 2025. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2022-49052
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0029
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Feb 26, 2025

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.17.6-1 | [DEBIAN-CVE-2022-49052](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49052.md) | Feb 26, 2025 |
| Linux | linux Debian 13.5 (trixie) | 5.17.6-1 | [DEBIAN-CVE-2022-49052](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49052.md) | Feb 26, 2025 |
| Linux | linux Debian 14 | 5.17.6-1 | [DEBIAN-CVE-2022-49052](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49052.md) | Feb 26, 2025 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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