GHSA-V5HF-7896-CMM7
Vulnerability from github – Published: 2026-07-25 12:31 – Updated: 2026-07-25 12:31In the Linux kernel, the following vulnerability has been resolved:
mm: page_ext: add count limit to page_ext_iter_next to prevent invalid PFN access
The page_ext iteration API does not validate if the PFN still belongs to a valid section while advancing the iterator. When dynamically adding memory in the hotplug path, it can lead to a NULL pointer dereference during page_ext_lookup at the boundary of the last valid section when iterator count equals __pgcount.
The for_each_page_ext() macro calls page_ext_iter_next() as its loop increment. for_each_page_ext() does a "__page_ext = page_ext_iter_next(&__iter)" at the end. This causes page_ext_iter_next() to increment iter->index past __pgcount and call page_ext_lookup(start_pfn + __pgcount). During memory hotplug (online), the PFN at start_pfn + __pgcount may belong to a section that has not yet been initialized, causing page_ext_lookup() to trigger a NULL pointer dereference.
[ 14.555124][ T846] Call trace: [ 14.555125][ T846] lookup_page_ext+0x6c/0x108 (P) [ 14.555127][ T846] page_ext_lookup+0x30/0x3c [ 14.555129][ T846] __reset_page_owner+0x11c/0x260 [ 14.571201][ T846] __free_pages_ok+0x5e8/0x8e0 [ 14.571204][ T846] __free_pages_core+0x78/0xf0 [ 14.571206][ T846] generic_online_page+0x14/0x24 [ 14.597782][ T846] online_pages+0x178/0x30c [ 14.597784][ T846] memory_block_change_state+0x284/0x32c [ 14.597787][ T846] memory_subsys_online+0x4c/0x64 [ 14.597789][ T846] device_online+0x88/0xb0 [ 14.597791][ T846] online_memory_block+0x30/0x40 [ 14.597793][ T846] walk_memory_blocks+0xac/0xe8 [ 14.597794][ T846] add_memory_resource+0x280/0x298 [ 14.656161][ T846] add_memory+0x60/0x98
Move the iteration boundary enforcement inside the iterator functions, so callers cannot inadvertently access beyond the requested range.
{
"affected": [],
"aliases": [
"CVE-2026-64295"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-25T10:17:10Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: page_ext: add count limit to page_ext_iter_next to prevent invalid PFN access\n\nThe page_ext iteration API does not validate if the PFN still belongs to a\nvalid section while advancing the iterator. When dynamically adding\nmemory in the hotplug path, it can lead to a NULL pointer dereference\nduring page_ext_lookup at the boundary of the last valid section when\niterator count equals __pgcount.\n\nThe for_each_page_ext() macro calls page_ext_iter_next() as its loop\nincrement. for_each_page_ext() does a \"__page_ext =\npage_ext_iter_next(\u0026__iter)\" at the end. This causes page_ext_iter_next()\nto increment iter-\u003eindex past __pgcount and call page_ext_lookup(start_pfn\n+ __pgcount). During memory hotplug (online), the PFN at start_pfn +\n__pgcount may belong to a section that has not yet been initialized,\ncausing page_ext_lookup() to trigger a NULL pointer dereference.\n\n[ 14.555124][ T846] Call trace:\n[ 14.555125][ T846] lookup_page_ext+0x6c/0x108 (P)\n[ 14.555127][ T846] page_ext_lookup+0x30/0x3c\n[ 14.555129][ T846] __reset_page_owner+0x11c/0x260\n[ 14.571201][ T846] __free_pages_ok+0x5e8/0x8e0\n[ 14.571204][ T846] __free_pages_core+0x78/0xf0\n[ 14.571206][ T846] generic_online_page+0x14/0x24\n[ 14.597782][ T846] online_pages+0x178/0x30c\n[ 14.597784][ T846] memory_block_change_state+0x284/0x32c\n[ 14.597787][ T846] memory_subsys_online+0x4c/0x64\n[ 14.597789][ T846] device_online+0x88/0xb0\n[ 14.597791][ T846] online_memory_block+0x30/0x40\n[ 14.597793][ T846] walk_memory_blocks+0xac/0xe8\n[ 14.597794][ T846] add_memory_resource+0x280/0x298\n[ 14.656161][ T846] add_memory+0x60/0x98\n\nMove the iteration boundary enforcement inside the iterator functions, so\ncallers cannot inadvertently access beyond the requested range.",
"id": "GHSA-v5hf-7896-cmm7",
"modified": "2026-07-25T12:31:29Z",
"published": "2026-07-25T12:31:29Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64295"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/377b1cd6bbcf327338cd951cc2fd74bc75540235"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8dcaa0f87a88d720d13106f3a306c6b61d189d86"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ffd017237cfe99e6e5602ab14179b0e6878a0840"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
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