ghsa-3f3w-qrjm-6m77
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
mm: cachestat: fix two shmem bugs
When cachestat on shmem races with swapping and invalidation, there are two possible bugs:
1) A swapin error can have resulted in a poisoned swap entry in the shmem inode's xarray. Calling get_shadow_from_swap_cache() on it will result in an out-of-bounds access to swapper_spaces[].
Validate the entry with non_swap_entry() before going further.
2) When we find a valid swap entry in the shmem's inode, the shadow entry in the swapcache might not exist yet: swap IO is still in progress and we're before __remove_mapping; swapin, invalidation, or swapoff have removed the shadow from swapcache after we saw the shmem swap entry.
This will send a NULL to workingset_test_recent(). The latter purely operates on pointer bits, so it won't crash - node 0, memcg ID 0, eviction timestamp 0, etc. are all valid inputs - but it's a bogus test. In theory that could result in a false "recently evicted" count.
Such a false positive wouldn't be the end of the world. But for code clarity and (future) robustness, be explicit about this case.
Bail on get_shadow_from_swap_cache() returning NULL.
{
"affected": [],
"aliases": [
"CVE-2024-35797"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-05-17T14:15:11Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: cachestat: fix two shmem bugs\n\nWhen cachestat on shmem races with swapping and invalidation, there\nare two possible bugs:\n\n1) A swapin error can have resulted in a poisoned swap entry in the\n shmem inode\u0027s xarray. Calling get_shadow_from_swap_cache() on it\n will result in an out-of-bounds access to swapper_spaces[].\n\n Validate the entry with non_swap_entry() before going further.\n\n2) When we find a valid swap entry in the shmem\u0027s inode, the shadow\n entry in the swapcache might not exist yet: swap IO is still in\n progress and we\u0027re before __remove_mapping; swapin, invalidation,\n or swapoff have removed the shadow from swapcache after we saw the\n shmem swap entry.\n\n This will send a NULL to workingset_test_recent(). The latter\n purely operates on pointer bits, so it won\u0027t crash - node 0, memcg\n ID 0, eviction timestamp 0, etc. are all valid inputs - but it\u0027s a\n bogus test. In theory that could result in a false \"recently\n evicted\" count.\n\n Such a false positive wouldn\u0027t be the end of the world. But for\n code clarity and (future) robustness, be explicit about this case.\n\n Bail on get_shadow_from_swap_cache() returning NULL.",
"id": "GHSA-3f3w-qrjm-6m77",
"modified": "2024-05-17T15:31:09Z",
"published": "2024-05-17T15:31:09Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-35797"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/24a0e73d544439bb9329fbbafac44299e548a677"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b79f9e1ff27c994a4c452235ba09e672ec698e23"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d5d39c707a4cf0bcc84680178677b97aa2cb2627"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d962f6c583458037dc7e529659b2b02b9dd3d94b"
}
],
"schema_version": "1.4.0",
"severity": []
}