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CVE-2024-39486— drm/drm_file: Fix pid refcounting race

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于存在pid引用计数竞争漏洞。

CVSS 7.8 · High EPSS 0.23% · P13

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 9

VendorProduct Version RangeStatus
Linux Linux 031ddd28008971cce0b5626379b910d0a05fb4dd< 16682588ead4a593cf1aebb33b36df4d1e9e4ffa affected
1c7a387ffef894b1ab3942f0482dac7a6e0a909c< 0acce2a5c619ef1abdee783d7fea5eac78ce4844 affected
1c7a387ffef894b1ab3942f0482dac7a6e0a909c< 4f2a129b33a2054e62273edd5a051c34c08d96e9 affected
6.6.9< 6.6.37 affected
6.7 affected
< 6.7 unaffected
6.6.37≤ 6.6.* unaffected
6.9.8≤ 6.9.* unaffected
… +1 more rows
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I. Basic Information for CVE-2024-39486

Vulnerability Information
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Vulnerability Title
drm/drm_file: Fix pid refcounting race
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于存在pid引用计数竞争漏洞。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 031ddd28008971cce0b5626379b910d0a05fb4dd ~ 16682588ead4a593cf1aebb33b36df4d1e9e4ffa -
Linux Linux 6.7 -

II. Public POCs for CVE-2024-39486

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III. Intelligence Information for CVE-2024-39486

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Other References for CVE-2024-39486 (3)

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2024-39486

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