CVE-2024-40899cachefiles: fix slab-use-after-free in cachefiles_ondemand_get_fd()
- 7.8HighCVSS base score
- 0.28%Exploitation in 30 daysEPSS · top 79% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In the Linux kernel, the following vulnerability has been resolved: cachefiles: fix slab-use-after-free in cachefiles_ondemand_get_fd() We got the following issue in a fuzz test of randomly issuing the restore command: ================================================================== BUG: KASAN: slab-use-after-free in cachefiles_ondemand_daemon_read+0x609/0xab0 Write of size 4 at addr ffff888109164a80 by task ondemand-04-dae/4962 CPU: 11 PID: 4962 Comm: ondemand-04-dae Not tainted 6.8.0-rc7-dirty #542 Call Trace: kasan_report+0x94/0xc0 cachefiles_ondemand_daemon_read+0x609/0xab0 vfs_read+0x169/0xb50 ksys_read+0xf5/0x1e0 Allocated by task 626: __kmalloc+0x1df/0x4b0 cachefiles_ondemand_send_req+0x24d/0x690 cachefiles_create_tmpfile+0x249/0xb30 cachefiles_create_file+0x6f/0x140 cachefiles_look_up_object+0x29c/0xa60 cachefiles_lookup_cookie+0x37d/0xca0 fscache_cookie_state_machine+0x43c/0x1230 [...] Freed by task 626: kfree+0xf1/0x2c0 cachefiles_ondemand_send_req+0x568/0x690 cachefiles_create_tmpfile+0x249/0xb30 cachefiles_create_file+0x6f/0x140 cachefiles_look_up_object+0x29c/0xa60 cachefiles_lookup_cookie+0x37d/0xca0 fscache_cookie_state_machine+0x43c/0x1230 [...] ================================================================== Following is the process that triggers the issue: mount | daemon_thread1 | daemon_thread2 ------------------------------------------------------------ cachefiles_ondemand_init_object cachefiles_ondemand_send_req REQ_A = kzalloc(sizeof(*req) + data_len) wait_for_completion(&REQ_A->done) cachefiles_daemon_read cachefiles_ondemand_daemon_read REQ_A = cachefiles_ondemand_select_req cachefiles_ondemand_get_fd copy_to_user(_buffer, msg, n) process_open_req(REQ_A) ------ restore ------ cachefiles_ondemand_restore xas_for_each(&xas, req, ULONG_MAX) xas_set_mark(&xas, CACHEFILES_REQ_NEW); cachefiles_daemon_read cachefiles_ondemand_daemon_read REQ_A = cachefiles_ondemand_select_req write(devfd, ("copen %u,%llu", msg->msg_id, size)); cachefiles_ondemand_copen xa_erase(&cache->reqs, id) complete(&REQ_A->done) kfree(REQ_A) cachefiles_ondemand_get_fd(REQ_A) fd = get_unused_fd_flags file = anon_inode_getfile fd_install(fd, file) load = (void *)REQ_A->msg.data; load->fd = fd; // load UAF !!! This issue is caused by issuing a restore command when the daemon is still alive, which results in a request being processed multiple times thus triggering a UAF. So to avoid this problem, add an additional reference count to cachefiles_req, which is held while waiting and reading, and then released when the waiting and reading is over. Note that since there is only one reference count for waiting, we need to avoid the same request being completed multiple times, so we can only complete the request if it is successfully removed from the xarray.
Timeline
ID reserved
By Linux
Published
- 22 months later
· 22 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.28% · top 79% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.
Affected products
- affected a0cc87f86698174aacc083c4652d2606007dd902 – < 99e9c5bd27ddefa0f9db88625bf5e31c1e833d62
- affected 9f5fa40f0924e9de85b16c6d1aea80327ce647d8 – < a6de82765e12fb1201ab607f0d3ffe3309b30fc0
- affected e73fa11a356ca0905c3cc648eaacc6f0f2d2c8b3 – < 1d902d9a3aa4f2a8bda698294e34be788be012fc
- affected e73fa11a356ca0905c3cc648eaacc6f0f2d2c8b3 – < de3e26f9e5b76fc628077578c001c4a51bf54d06
- affected 6.8
- unaffected < 6.8
- unaffected 6.9.6 – ≤ 6.9.*
- unaffected 6.10 – ≤ *
References
References5
- https://git.kernel.org/stable/c/99e9c5bd27ddefa0f9db88625bf5e31c1e833d62 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/a6de82765e12fb1201ab607f0d3ffe3309b30fc0 (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/1d902d9a3aa4f2a8bda698294e34be788be012fc (opens in a new tab)x_transferred
- https://git.kernel.org/stable/c/de3e26f9e5b76fc628077578c001c4a51bf54d06 (opens in a new tab)x_transferred
- https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2024-38710 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2024-40899)Record last updated .