CVE-2024-26960

Advisory lineage Upstream: 0 Downstream: 36
Modified
Published: 01 May 2024, 05:19
Last modified:12 May 2026, 11:50

Vulnerability Summary

Overall Risk (default)
low
22/100
CVSS Score
5.5 MEDIUM
v3.1 (cve.org)
EPSS Score
<0.01% LOW
0% probability 0.00%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

01 May 2024, 05:19
Published
Vulnerability first disclosed
12 May 2026, 11:50
Last Modified
Vulnerability information updated

Description

In the Linux kernel, the following vulnerability has been resolved: mm: swap: fix race between free_swap_and_cache() and swapoff() There was previously a theoretical window where swapoff() could run and teardown a swap_info_struct while a call to free_swap_and_cache() was running in another thread. This could cause, amongst other bad possibilities, swap_page_trans_huge_swapped() (called by free_swap_and_cache()) to access the freed memory for swap_map. This is a theoretical problem and I haven't been able to provoke it from a test case. But there has been agreement based on code review that this is possible (see link below). Fix it by using get_swap_device()/put_swap_device(), which will stall swapoff(). There was an extra check in _swap_info_get() to confirm that the swap entry was not free. This isn't present in get_swap_device() because it doesn't make sense in general due to the race between getting the reference and swapoff. So I've added an equivalent check directly in free_swap_and_cache(). Details of how to provoke one possible issue (thanks to David Hildenbrand for deriving this): --8<----- __swap_entry_free() might be the last user and result in "count == SWAP_HAS_CACHE". swapoff->try_to_unuse() will stop as soon as soon as si->inuse_pages==0. So the question is: could someone reclaim the folio and turn si->inuse_pages==0, before we completed swap_page_trans_huge_swapped(). Imagine the following: 2 MiB folio in the swapcache. Only 2 subpages are still references by swap entries. Process 1 still references subpage 0 via swap entry. Process 2 still references subpage 1 via swap entry. Process 1 quits. Calls free_swap_and_cache(). -> count == SWAP_HAS_CACHE [then, preempted in the hypervisor etc.] Process 2 quits. Calls free_swap_and_cache(). -> count == SWAP_HAS_CACHE Process 2 goes ahead, passes swap_page_trans_huge_swapped(), and calls __try_to_reclaim_swap(). __try_to_reclaim_swap()->folio_free_swap()->delete_from_swap_cache()-> put_swap_folio()->free_swap_slot()->swapcache_free_entries()-> swap_entry_free()->swap_range_free()-> ... WRITE_ONCE(si->inuse_pages, si->inuse_pages - nr_entries); What stops swapoff to succeed after process 2 reclaimed the swap cache but before process1 finished its call to swap_page_trans_huge_swapped()? --8<-----

CVSS Metrics

  • v3.1•MEDIUM•Score: 5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS Trends

Current EPSS score: 0.01%• Percentile: 0%

Techniques & Countermeasures

  • CWE-362•Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

    The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Systems

  • debian•debian_linux

    10.0

  • linux•linux

    ≥ 7c00bafee87c7bac7ed9eced7c161f8e5332cb4e, < d85c11c97ecf92d47a4b29e3faca714dc1f18d0d | ≥ 7c00bafee87c7bac7ed9eced7c161f8e5332cb4e, < 2da5568ee222ce0541bfe446a07998f92ed1643e | ≥ 7c00bafee87c7bac7ed9eced7c161f8e5332cb4e, < 1ede7f1d7eed1738d1b9333fd1e152ccb450b86a | ≥ 7c00bafee87c7bac7ed9eced7c161f8e5332cb4e, < 0f98f6d2fb5fad00f8299b84b85b6bc1b6d7d19a | ≥ 7c00bafee87c7bac7ed9eced7c161f8e5332cb4e, < 3ce4c4c653e4e478ecb15d3c88e690f12cbf6b39 | ≥ 7c00bafee87c7bac7ed9eced7c161f8e5332cb4e, < 363d17e7f7907c8e27a9e86968af0eaa2301787b | ≥ 7c00bafee87c7bac7ed9eced7c161f8e5332cb4e, < 82b1c07a0af603e3c47b906c8e991dc96f01688e | 4.11

  • linux•linux_kernel

    ≥ 4.11, < 5.10.215 | ≥ 5.11, < 5.15.154 | ≥ 5.16, < 6.1.84 | ≥ 6.2, < 6.6.24 | ≥ 6.7, < 6.7.12 | ≥ 6.8, < 6.8.3

References (9)