CVE - CVE-2024-39486

CVE-ID
CVE-2024-39486	Learn more at National Vulnerability Database (NVD) • CVSS Severity Rating • Fix Information • Vulnerable Software Versions • SCAP Mappings • CPE Information
Description
In the Linux kernel, the following vulnerability has been resolved: drm/drm_file: Fix pid refcounting race <maarten.lankhorst@linux.intel.com>, Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de> filp->pid is supposed to be a refcounted pointer; however, before this patch, drm_file_update_pid() only increments the refcount of a struct pid after storing a pointer to it in filp->pid and dropping the dev->filelist_mutex, making the following race possible: process A process B ========= ========= begin drm_file_update_pid mutex_lock(&dev->filelist_mutex) rcu_replace_pointer(filp->pid, <pid B>, 1) mutex_unlock(&dev->filelist_mutex) begin drm_file_update_pid mutex_lock(&dev->filelist_mutex) rcu_replace_pointer(filp->pid, <pid A>, 1) mutex_unlock(&dev->filelist_mutex) get_pid(<pid A>) synchronize_rcu() put_pid(<pid B>) * pid B reaches refcount 0 and is freed here * get_pid(<pid B>) * UAF * synchronize_rcu() put_pid(<pid A>) As far as I know, this race can only occur with CONFIG_PREEMPT_RCU=y because it requires RCU to detect a quiescent state in code that is not explicitly calling into the scheduler. This race leads to use-after-free of a "struct pid". It is probably somewhat hard to hit because process A has to pass through a synchronize_rcu() operation while process B is between mutex_unlock() and get_pid(). Fix it by ensuring that by the time a pointer to the current task's pid is stored in the file, an extra reference to the pid has been taken. This fix also removes the condition for synchronize_rcu(); I think that optimization is unnecessary complexity, since in that case we would usually have bailed out on the lockless check above.
References
Note: References are provided for the convenience of the reader to help distinguish between vulnerabilities. The list is not intended to be complete.
MISC:https://git.kernel.org/stable/c/0acce2a5c619ef1abdee783d7fea5eac78ce4844 URL:https://git.kernel.org/stable/c/0acce2a5c619ef1abdee783d7fea5eac78ce4844 MISC:https://git.kernel.org/stable/c/16682588ead4a593cf1aebb33b36df4d1e9e4ffa URL:https://git.kernel.org/stable/c/16682588ead4a593cf1aebb33b36df4d1e9e4ffa MISC:https://git.kernel.org/stable/c/4f2a129b33a2054e62273edd5a051c34c08d96e9 URL:https://git.kernel.org/stable/c/4f2a129b33a2054e62273edd5a051c34c08d96e9
Assigning CNA
kernel.org
Date Record Created
20240625	Disclaimer: The record creation date may reflect when the CVE ID was allocated or reserved, and does not necessarily indicate when this vulnerability was discovered, shared with the affected vendor, publicly disclosed, or updated in CVE.
Phase (Legacy)
Assigned (20240625)
Votes (Legacy)

Comments (Legacy)

Proposed (Legacy)
N/A
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