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CVE-2024-39486
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CVE-2024-39486
MITRE ATT&CK
Collection
Command and Control
Credential Access
Defense Evasion
Discovery
Execution
Exfiltration
Impact
Initial Access
Lateral Movement
Persistence
Privilege Escalation
Topic Tags
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.
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General Information
Vendors
- linux
Products
- linux kernel,
- linux kernel 6.10
References
Additional Info
Technical Analysis
Report as Emergent Threat Response
Report as Exploited in the Wild
CVE ID
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