ghsa-chrh-m3h6-4898
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
x86/sgx: Prevent attempts to reclaim poisoned pages
TL;DR: SGX page reclaim touches the page to copy its contents to secondary storage. SGX instructions do not gracefully handle machine checks. Despite this, the existing SGX code will try to reclaim pages that it knows are poisoned. Avoid even trying to reclaim poisoned pages.
The longer story:
Pages used by an enclave only get epc_page->poison set in arch_memory_failure() but they currently stay on sgx_active_page_list until sgx_encl_release(), with the SGX_EPC_PAGE_RECLAIMER_TRACKED flag untouched.
epc_page->poison is not checked in the reclaimer logic meaning that, if other conditions are met, an attempt will be made to reclaim an EPC page that was poisoned. This is bad because 1. we don't want that page to end up added to another enclave and 2. it is likely to cause one core to shut down and the kernel to panic.
Specifically, reclaiming uses microcode operations including "EWB" which accesses the EPC page contents to encrypt and write them out to non-SGX memory. Those operations cannot handle MCEs in their accesses other than by putting the executing core into a special shutdown state (affecting both threads with HT.) The kernel will subsequently panic on the remaining cores seeing the core didn't enter MCE handler(s) in time.
Call sgx_unmark_page_reclaimable() to remove the affected EPC page from sgx_active_page_list on memory error to stop it being considered for reclaiming.
Testing epc_page->poison in sgx_reclaim_pages() would also work but I assume it's better to add code in the less likely paths.
The affected EPC page is not added to &node->sgx_poison_page_list until later in sgx_encl_release()->sgx_free_epc_page() when it is EREMOVEd. Membership on other lists doesn't change to avoid changing any of the lists' semantics except for sgx_active_page_list. There's a "TBD" comment in arch_memory_failure() about pre-emptive actions, the goal here is not to address everything that it may imply.
This also doesn't completely close the time window when a memory error notification will be fatal (for a not previously poisoned EPC page) -- the MCE can happen after sgx_reclaim_pages() has selected its candidates or even inside a microcode operation (actually easy to trigger due to the amount of time spent in them.)
The spinlock in sgx_unmark_page_reclaimable() is safe because memory_failure() runs in process context and no spinlocks are held, explicitly noted in a mm/memory-failure.c comment.
{
"affected": [],
"aliases": [
"CVE-2025-38334"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-07-10T09:15:27Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/sgx: Prevent attempts to reclaim poisoned pages\n\nTL;DR: SGX page reclaim touches the page to copy its contents to\nsecondary storage. SGX instructions do not gracefully handle machine\nchecks. Despite this, the existing SGX code will try to reclaim pages\nthat it _knows_ are poisoned. Avoid even trying to reclaim poisoned pages.\n\nThe longer story:\n\nPages used by an enclave only get epc_page-\u003epoison set in\narch_memory_failure() but they currently stay on sgx_active_page_list until\nsgx_encl_release(), with the SGX_EPC_PAGE_RECLAIMER_TRACKED flag untouched.\n\nepc_page-\u003epoison is not checked in the reclaimer logic meaning that, if other\nconditions are met, an attempt will be made to reclaim an EPC page that was\npoisoned. This is bad because 1. we don\u0027t want that page to end up added\nto another enclave and 2. it is likely to cause one core to shut down\nand the kernel to panic.\n\nSpecifically, reclaiming uses microcode operations including \"EWB\" which\naccesses the EPC page contents to encrypt and write them out to non-SGX\nmemory. Those operations cannot handle MCEs in their accesses other than\nby putting the executing core into a special shutdown state (affecting\nboth threads with HT.) The kernel will subsequently panic on the\nremaining cores seeing the core didn\u0027t enter MCE handler(s) in time.\n\nCall sgx_unmark_page_reclaimable() to remove the affected EPC page from\nsgx_active_page_list on memory error to stop it being considered for\nreclaiming.\n\nTesting epc_page-\u003epoison in sgx_reclaim_pages() would also work but I assume\nit\u0027s better to add code in the less likely paths.\n\nThe affected EPC page is not added to \u0026node-\u003esgx_poison_page_list until\nlater in sgx_encl_release()-\u003esgx_free_epc_page() when it is EREMOVEd.\nMembership on other lists doesn\u0027t change to avoid changing any of the\nlists\u0027 semantics except for sgx_active_page_list. There\u0027s a \"TBD\" comment\nin arch_memory_failure() about pre-emptive actions, the goal here is not\nto address everything that it may imply.\n\nThis also doesn\u0027t completely close the time window when a memory error\nnotification will be fatal (for a not previously poisoned EPC page) --\nthe MCE can happen after sgx_reclaim_pages() has selected its candidates\nor even *inside* a microcode operation (actually easy to trigger due to\nthe amount of time spent in them.)\n\nThe spinlock in sgx_unmark_page_reclaimable() is safe because\nmemory_failure() runs in process context and no spinlocks are held,\nexplicitly noted in a mm/memory-failure.c comment.",
"id": "GHSA-chrh-m3h6-4898",
"modified": "2025-07-10T09:32:31Z",
"published": "2025-07-10T09:32:31Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38334"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/00a88e9ea1b170d579c56327c38f7e8cf689df87"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/31dcbac94bfeabb86bf85b0c36803fdd6536437b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/62b62a2a6dc51ed6e8e334861f04220c9cf8106a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dc5de5bd6deabd327ced2b2b1d0b4f14cd146afe"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ed16618c380c32c68c06186d0ccbb0d5e0586e59"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.