{"id":"DEBIAN-CVE-2024-26960","details":"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\u003c-----  __swap_entry_free() might be the last user and result in \"count == SWAP_HAS_CACHE\".  swapoff-\u003etry_to_unuse() will stop as soon as soon as si-\u003einuse_pages==0.  So the question is: could someone reclaim the folio and turn si-\u003einuse_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(). -\u003e count == SWAP_HAS_CACHE [then, preempted in the hypervisor etc.]  Process 2 quits. Calls free_swap_and_cache(). -\u003e count == SWAP_HAS_CACHE  Process 2 goes ahead, passes swap_page_trans_huge_swapped(), and calls __try_to_reclaim_swap().  __try_to_reclaim_swap()-\u003efolio_free_swap()-\u003edelete_from_swap_cache()-\u003e put_swap_folio()-\u003efree_swap_slot()-\u003eswapcache_free_entries()-\u003e swap_entry_free()-\u003eswap_range_free()-\u003e ... WRITE_ONCE(si-\u003einuse_pages, si-\u003einuse_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\u003c-----","modified":"2026-09-15T09:02:55.974469773Z","published":"2024-05-01T06:15:12.323Z","upstream":["CVE-2024-26960"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2024-26960"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.85-1"}]}],"versions":["6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-26960.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.7.12-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-26960.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.7.12-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-26960.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}