GHSA-GCPR-PGRP-45FP
Vulnerability from github – Published: 2024-09-04 21:30 – Updated: 2025-11-04 00:31In the Linux kernel, the following vulnerability has been resolved:
fs/netfs/fscache_cookie: add missing "n_accesses" check
This fixes a NULL pointer dereference bug due to a data race which looks like this:
BUG: kernel NULL pointer dereference, address: 0000000000000008 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI CPU: 33 PID: 16573 Comm: kworker/u97:799 Not tainted 6.8.7-cm4all1-hp+ #43 Hardware name: HP ProLiant DL380 Gen9/ProLiant DL380 Gen9, BIOS P89 10/17/2018 Workqueue: events_unbound netfs_rreq_write_to_cache_work RIP: 0010:cachefiles_prepare_write+0x30/0xa0 Code: 57 41 56 45 89 ce 41 55 49 89 cd 41 54 49 89 d4 55 53 48 89 fb 48 83 ec 08 48 8b 47 08 48 83 7f 10 00 48 89 34 24 48 8b 68 20 <48> 8b 45 08 4c 8b 38 74 45 49 8b 7f 50 e8 4e a9 b0 ff 48 8b 73 10 RSP: 0018:ffffb4e78113bde0 EFLAGS: 00010286 RAX: ffff976126be6d10 RBX: ffff97615cdb8438 RCX: 0000000000020000 RDX: ffff97605e6c4c68 RSI: ffff97605e6c4c60 RDI: ffff97615cdb8438 RBP: 0000000000000000 R08: 0000000000278333 R09: 0000000000000001 R10: ffff97605e6c4600 R11: 0000000000000001 R12: ffff97605e6c4c68 R13: 0000000000020000 R14: 0000000000000001 R15: ffff976064fe2c00 FS: 0000000000000000(0000) GS:ffff9776dfd40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000008 CR3: 000000005942c002 CR4: 00000000001706f0 Call Trace: ? __die+0x1f/0x70 ? page_fault_oops+0x15d/0x440 ? search_module_extables+0xe/0x40 ? fixup_exception+0x22/0x2f0 ? exc_page_fault+0x5f/0x100 ? asm_exc_page_fault+0x22/0x30 ? cachefiles_prepare_write+0x30/0xa0 netfs_rreq_write_to_cache_work+0x135/0x2e0 process_one_work+0x137/0x2c0 worker_thread+0x2e9/0x400 ? __pfx_worker_thread+0x10/0x10 kthread+0xcc/0x100 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x30/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1b/0x30 Modules linked in: CR2: 0000000000000008 ---[ end trace 0000000000000000 ]---
This happened because fscache_cookie_state_machine() was slow and was still running while another process invoked fscache_unuse_cookie(); this led to a fscache_cookie_lru_do_one() call, setting the FSCACHE_COOKIE_DO_LRU_DISCARD flag, which was picked up by fscache_cookie_state_machine(), withdrawing the cookie via cachefiles_withdraw_cookie(), clearing cookie->cache_priv.
At the same time, yet another process invoked cachefiles_prepare_write(), which found a NULL pointer in this code line:
struct cachefiles_object *object = cachefiles_cres_object(cres);
The next line crashes, obviously:
struct cachefiles_cache *cache = object->volume->cache;
During cachefiles_prepare_write(), the "n_accesses" counter is non-zero (via fscache_begin_operation()). The cookie must not be withdrawn until it drops to zero.
The counter is checked by fscache_cookie_state_machine() before switching to FSCACHE_COOKIE_STATE_RELINQUISHING and FSCACHE_COOKIE_STATE_WITHDRAWING (in "case FSCACHE_COOKIE_STATE_FAILED"), but not for FSCACHE_COOKIE_STATE_LRU_DISCARDING ("case FSCACHE_COOKIE_STATE_ACTIVE").
This patch adds the missing check. With a non-zero access counter, the function returns and the next fscache_end_cookie_access() call will queue another fscache_cookie_state_machine() call to handle the still-pending FSCACHE_COOKIE_DO_LRU_DISCARD.
{
"affected": [],
"aliases": [
"CVE-2024-45000"
],
"database_specific": {
"cwe_ids": [
"CWE-476"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-09-04T20:15:08Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/netfs/fscache_cookie: add missing \"n_accesses\" check\n\nThis fixes a NULL pointer dereference bug due to a data race which\nlooks like this:\n\n BUG: kernel NULL pointer dereference, address: 0000000000000008\n #PF: supervisor read access in kernel mode\n #PF: error_code(0x0000) - not-present page\n PGD 0 P4D 0\n Oops: 0000 [#1] SMP PTI\n CPU: 33 PID: 16573 Comm: kworker/u97:799 Not tainted 6.8.7-cm4all1-hp+ #43\n Hardware name: HP ProLiant DL380 Gen9/ProLiant DL380 Gen9, BIOS P89 10/17/2018\n Workqueue: events_unbound netfs_rreq_write_to_cache_work\n RIP: 0010:cachefiles_prepare_write+0x30/0xa0\n Code: 57 41 56 45 89 ce 41 55 49 89 cd 41 54 49 89 d4 55 53 48 89 fb 48 83 ec 08 48 8b 47 08 48 83 7f 10 00 48 89 34 24 48 8b 68 20 \u003c48\u003e 8b 45 08 4c 8b 38 74 45 49 8b 7f 50 e8 4e a9 b0 ff 48 8b 73 10\n RSP: 0018:ffffb4e78113bde0 EFLAGS: 00010286\n RAX: ffff976126be6d10 RBX: ffff97615cdb8438 RCX: 0000000000020000\n RDX: ffff97605e6c4c68 RSI: ffff97605e6c4c60 RDI: ffff97615cdb8438\n RBP: 0000000000000000 R08: 0000000000278333 R09: 0000000000000001\n R10: ffff97605e6c4600 R11: 0000000000000001 R12: ffff97605e6c4c68\n R13: 0000000000020000 R14: 0000000000000001 R15: ffff976064fe2c00\n FS: 0000000000000000(0000) GS:ffff9776dfd40000(0000) knlGS:0000000000000000\n CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n CR2: 0000000000000008 CR3: 000000005942c002 CR4: 00000000001706f0\n Call Trace:\n \u003cTASK\u003e\n ? __die+0x1f/0x70\n ? page_fault_oops+0x15d/0x440\n ? search_module_extables+0xe/0x40\n ? fixup_exception+0x22/0x2f0\n ? exc_page_fault+0x5f/0x100\n ? asm_exc_page_fault+0x22/0x30\n ? cachefiles_prepare_write+0x30/0xa0\n netfs_rreq_write_to_cache_work+0x135/0x2e0\n process_one_work+0x137/0x2c0\n worker_thread+0x2e9/0x400\n ? __pfx_worker_thread+0x10/0x10\n kthread+0xcc/0x100\n ? __pfx_kthread+0x10/0x10\n ret_from_fork+0x30/0x50\n ? __pfx_kthread+0x10/0x10\n ret_from_fork_asm+0x1b/0x30\n \u003c/TASK\u003e\n Modules linked in:\n CR2: 0000000000000008\n ---[ end trace 0000000000000000 ]---\n\nThis happened because fscache_cookie_state_machine() was slow and was\nstill running while another process invoked fscache_unuse_cookie();\nthis led to a fscache_cookie_lru_do_one() call, setting the\nFSCACHE_COOKIE_DO_LRU_DISCARD flag, which was picked up by\nfscache_cookie_state_machine(), withdrawing the cookie via\ncachefiles_withdraw_cookie(), clearing cookie-\u003ecache_priv.\n\nAt the same time, yet another process invoked\ncachefiles_prepare_write(), which found a NULL pointer in this code\nline:\n\n struct cachefiles_object *object = cachefiles_cres_object(cres);\n\nThe next line crashes, obviously:\n\n struct cachefiles_cache *cache = object-\u003evolume-\u003ecache;\n\nDuring cachefiles_prepare_write(), the \"n_accesses\" counter is\nnon-zero (via fscache_begin_operation()). The cookie must not be\nwithdrawn until it drops to zero.\n\nThe counter is checked by fscache_cookie_state_machine() before\nswitching to FSCACHE_COOKIE_STATE_RELINQUISHING and\nFSCACHE_COOKIE_STATE_WITHDRAWING (in \"case\nFSCACHE_COOKIE_STATE_FAILED\"), but not for\nFSCACHE_COOKIE_STATE_LRU_DISCARDING (\"case\nFSCACHE_COOKIE_STATE_ACTIVE\").\n\nThis patch adds the missing check. With a non-zero access counter,\nthe function returns and the next fscache_end_cookie_access() call\nwill queue another fscache_cookie_state_machine() call to handle the\nstill-pending FSCACHE_COOKIE_DO_LRU_DISCARD.",
"id": "GHSA-gcpr-pgrp-45fp",
"modified": "2025-11-04T00:31:23Z",
"published": "2024-09-04T21:30:32Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-45000"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0a4d41fa14b2a0efd40e350cfe8ec6a4c998ac1d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b8a50877f68efdcc0be3fcc5116e00c31b90e45b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dfaa39b05a6cf34a16c525a2759ee6ab26b5fef6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f71aa06398aabc2e3eaac25acdf3d62e0094ba70"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
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- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.