CVE-2024-56640
Linux Kernel use-after-free
- Published27 Dec 2024
Description
In the Linux kernel, the following vulnerability has been resolved: net/smc: fix LGR and link use-after-free issue We encountered a LGR/link use-after-free issue, which manifested as the LGR/link refcnt reaching 0 early and entering the clear process, making resource access unsafe. refcount_t: addition on 0; use-after-free. WARNING: CPU: 14 PID: 107447 at lib/refcount.c:25 refcount_warn_saturate+0x9c/0x140 Workqueue: events smc_lgr_terminate_work [smc] Call trace: refcount_warn_saturate+0x9c/0x140 __smc_lgr_terminate.part.45+0x2a8/0x370 [smc] smc_lgr_terminate_work+0x28/0x30 [smc] process_one_work+0x1b8/0x420 worker_thread+0x158/0x510 kthread+0x114/0x118 or refcount_t: underflow; use-after-free. WARNING: CPU: 6 PID: 93140 at lib/refcount.c:28 refcount_warn_saturate+0xf0/0x140 Workqueue: smc_hs_wq smc_listen_work [smc] Call trace: refcount_warn_saturate+0xf0/0x140 smcr_link_put+0x1cc/0x1d8 [smc] smc_conn_free+0x110/0x1b0 [smc] smc_conn_abort+0x50/0x60 [smc] smc_listen_find_device+0x75c/0x790 [smc] smc_listen_work+0x368/0x8a0 [smc] process_one_work+0x1b8/0x420 worker_thread+0x158/0x510 kthread+0x114/0x118 It is caused by repeated release of LGR/link refcnt. One suspect is that smc_conn_free() is called repeatedly because some smc_conn_free() from server listening path are not protected by sock lock. e.g. Calls under socklock | smc_listen_work ------------------------------------------------------- lock_sock(sk) | smc_conn_abort smc_conn_free | \- smc_conn_free \- smcr_link_put | \- smcr_link_put (duplicated) release_sock(sk) So here add sock lock protection in smc_listen_work() path, making it exclusive with other connection operations.
CVSS 3.1 breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HAffected products
Remediation
- https://git.kernel.org/stable/c/0cf598548a6c36d90681d53c6b77d52363f2f295
- https://git.kernel.org/stable/c/2c7f14ed9c19ec0f149479d1c2842ec1f9bf76d7
- https://git.kernel.org/stable/c/673d606683ac70bc074ca6676b938bff18635226
- https://git.kernel.org/stable/c/6f0ae06a234a78ae137064f2c89135ac078a00eb
- https://git.kernel.org/stable/c/f502a88fdd415647a1f2dc45fac71b9c522a052b
References
- https://git.kernel.org/stable/c/0cf598548a6c36d90681d53c6b77d52363f2f295
- https://git.kernel.org/stable/c/2c7f14ed9c19ec0f149479d1c2842ec1f9bf76d7
- https://git.kernel.org/stable/c/673d606683ac70bc074ca6676b938bff18635226
- https://git.kernel.org/stable/c/6f0ae06a234a78ae137064f2c89135ac078a00eb
- https://git.kernel.org/stable/c/f502a88fdd415647a1f2dc45fac71b9c522a052b
- https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html
Related CVEs
Recent high-severity vulnerabilities sharing a weakness type.
Frequently asked
Is CVE-2024-56640 being actively exploited?
CVE-2024-56640 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.62%.
How severe is CVE-2024-56640?
CVE-2024-56640 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.62% probability of exploitation.
Which products are affected by CVE-2024-56640?
Affected products include Linux Kernel.
How do I fix CVE-2024-56640?
Upgrade affected software to a fixed version, for example Linux Kernel 5.15.174 or later, then confirm no affected versions remain in your inventory.
How Secuno handles this
Secuno correlates vulnerabilities like CVE-2024-56640 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.
Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.