{"id":"CVE-2024-26960","revision":"21ed8ac66aa947e28309ebd98477d396","records":[{"revision":"21ed8ac66aa947e28309ebd98477d396","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2024-26960","aliases":[],"title":"mm: swap: fix race between free_swap_and_cache() and swapoff()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm: swap: fix race between free_swap_and_cache() and swapoff()\n\nThere was previously a theoretical window where swapoff() could run and\nteardown a swap_info_struct while a call to free_swap_and_cache() was\nrunning in another thread.  This could cause, amongst other bad\npossibilities, swap_page_trans_huge_swapped() (called by\nfree_swap_and_cache()) to access the freed memory for swap_map.\n\nThis is a theoretical problem and I haven't been able to provoke it from a\ntest case.  But there has been agreement based on code review that this is\npossible (see link below).\n\nFix it by using get_swap_device()/put_swap_device(), which will stall\nswapoff().  There was an extra check in _swap_info_get() to confirm that\nthe swap entry was not free.  This isn't present in get_swap_device()\nbecause it doesn't make sense in general due to the race between getting\nthe reference and swapoff.  So I've added an equivalent check directly in\nfree_swap_and_cache().\n\nDetails of how to provoke one possible issue (thanks to David Hildenbrand\nfor deriving this):\n\n--8<-----\n\n__swap_entry_free() might be the last user and result in\n\"count == SWAP_HAS_CACHE\".\n\nswapoff->try_to_unuse() will stop as soon as soon as si->inuse_pages==0.\n\nSo the question is: could someone reclaim the folio and turn\nsi->inuse_pages==0, before we completed swap_page_trans_huge_swapped().\n\nImagine the following: 2 MiB folio in the swapcache. Only 2 subpages are\nstill references by swap entries.\n\nProcess 1 still references subpage 0 via swap entry.\nProcess 2 still references subpage 1 via swap entry.\n\nProcess 1 quits. Calls free_swap_and_cache().\n-> count == SWAP_HAS_CACHE\n[then, preempted in the hypervisor etc.]\n\nProcess 2 quits. Calls free_swap_and_cache().\n-> count == SWAP_HAS_CACHE\n\nProcess 2 goes ahead, passes swap_page_trans_huge_swapped(), and calls\n__try_to_reclaim_swap().\n\n__try_to_reclaim_swap()->folio_free_swap()->delete_from_swap_cache()->\nput_swap_folio()->free_swap_slot()->swapcache_free_entries()->\nswap_entry_free()->swap_range_free()->\n...\nWRITE_ONCE(si->inuse_pages, si->inuse_pages - nr_entries);\n\nWhat stops swapoff to succeed after process 2 reclaimed the swap cache\nbut before process1 finished its call to swap_page_trans_huge_swapped()?\n\n--8<-----","state":0,"publishedAt":"2024-05-01T05:19:12.112+00:00","modifiedAt":"2026-10-15T00:39:36.857+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"mm/swapfile.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"7c00bafee87c7bac7ed9eced7c161f8e5332cb4e\",\n                            \"lessThan\": \"d85c11c97ecf92d47a4b29e3faca714dc1f18d0d\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"7c00bafee87c7bac7ed9eced7c161f8e5332cb4e\",\n                            \"lessThan\": \"2da5568ee222ce0541bfe446a07998f92ed1643e\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"7c00bafee87c7bac7ed9eced7c161f8e5332cb4e\",\n                            \"lessThan\": \"1ede7f1d7eed1738d1b9333fd1e152ccb450b86a\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"7c00bafee87c7bac7ed9eced7c161f8e5332cb4e\",\n                            \"lessThan\": \"0f98f6d2fb5fad00f8299b84b85b6bc1b6d7d19a\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"7c00bafee87c7bac7ed9eced7c161f8e5332cb4e\",\n                            \"lessThan\": \"3ce4c4c653e4e478ecb15d3c88e690f12cbf6b39\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"7c00bafee87c7bac7ed9eced7c161f8e5332cb4e\",\n                            \"lessThan\": \"363d17e7f7907c8e27a9e86968af0eaa2301787b\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"7c00bafee87c7bac7ed9eced7c161f8e5332cb4e\",\n                            \"lessThan\": \"82b1c07a0af603e3c47b906c8e991dc96f01688e\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"mm/swapfile.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"4.11\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"4.11\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.215\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.154\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.84\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.24\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.7.12\",\n                            \"lessThanOrEqual\": \"6.7.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.8.3\",\n                            \"lessThanOrEqual\": \"6.8.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.9\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/d85c11c97ecf92d47a4b29e3faca714dc1f18d0d","https://git.kernel.org/stable/c/2da5568ee222ce0541bfe446a07998f92ed1643e","https://git.kernel.org/stable/c/1ede7f1d7eed1738d1b9333fd1e152ccb450b86a","https://git.kernel.org/stable/c/0f98f6d2fb5fad00f8299b84b85b6bc1b6d7d19a","https://git.kernel.org/stable/c/3ce4c4c653e4e478ecb15d3c88e690f12cbf6b39","https://git.kernel.org/stable/c/363d17e7f7907c8e27a9e86968af0eaa2301787b","https://git.kernel.org/stable/c/82b1c07a0af603e3c47b906c8e991dc96f01688e"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2024-26960","license":"CVE Program Terms of Use","key":"cve-program:CVE-2024-26960","identifiers":["CVE-2024-26960"]},"retained":false,"historicalAffected":[]}],"coverage":[]}