{"cve":"CVE-2024-39486","nvd":{"published":"2024-07-06T10:15:03.393","modified":"2026-08-04T11:18:59.807","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/drm_file: Fix pid refcounting race\n\n<maarten.lankhorst@linux.intel.com>, Maxime Ripard\n<mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>\n\nfilp->pid is supposed to be a refcounted pointer; however, before this\npatch, drm_file_update_pid() only increments the refcount of a struct\npid after storing a pointer to it in filp->pid and dropping the\ndev->filelist_mutex, making the following race possible:\n\nprocess A               process B\n=========               =========\n                        begin drm_file_update_pid\n                        mutex_lock(&dev->filelist_mutex)\n                        rcu_replace_pointer(filp->pid, <pid B>, 1)\n                        mutex_unlock(&dev->filelist_mutex)\nbegin drm_file_update_pid\nmutex_lock(&dev->filelist_mutex)\nrcu_replace_pointer(filp->pid, <pid A>, 1)\nmutex_unlock(&dev->filelist_mutex)\nget_pid(<pid A>)\nsynchronize_rcu()\nput_pid(<pid B>)   *** pid B reaches refcount 0 and is freed here ***\n                        get_pid(<pid B>)   *** UAF ***\n                        synchronize_rcu()\n                        put_pid(<pid A>)\n\nAs far as I know, this race can only occur with CONFIG_PREEMPT_RCU=y\nbecause it requires RCU to detect a quiescent state in code that is not\nexplicitly calling into the scheduler.\n\nThis race leads to use-after-free of a \"struct pid\".\nIt is probably somewhat hard to hit because process A has to pass\nthrough a synchronize_rcu() operation while process B is between\nmutex_unlock() and get_pid().\n\nFix it by ensuring that by the time a pointer to the current task's pid\nis stored in the file, an extra reference to the pid has been taken.\n\nThis fix also removes the condition for synchronize_rcu(); I think\nthat optimization is unnecessary complexity, since in that case we\nwould usually have bailed out on the lockless check above.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.0},"cwes":["CWE-416"],"references":["https://git.kernel.org/stable/c/0acce2a5c619ef1abdee783d7fea5eac78ce4844","https://git.kernel.org/stable/c/16682588ead4a593cf1aebb33b36df4d1e9e4ffa","https://git.kernel.org/stable/c/4f2a129b33a2054e62273edd5a051c34c08d96e9","https://git.kernel.org/stable/c/0acce2a5c619ef1abdee783d7fea5eac78ce4844","https://git.kernel.org/stable/c/16682588ead4a593cf1aebb33b36df4d1e9e4ffa"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:52:00.836172422+00:00"},"epss":{"cve":"CVE-2024-39486","score":0.00229,"percentile":0.13792,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}