{
    "data_version": "4.0",
    "data_type": "CVE",
    "data_format": "MITRE",
    "CVE_data_meta": {
        "ID": "CVE-2024-39486",
        "ASSIGNER": "cve@kernel.org",
        "STATE": "PUBLIC"
    },
    "description": {
        "description_data": [
            {
                "lang": "eng",
                "value": "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."
            }
        ]
    },
    "problemtype": {
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                "description": [
                    {
                        "lang": "eng",
                        "value": "n/a"
                    }
                ]
            }
        ]
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    "affects": {
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                    "vendor_name": "Linux",
                    "product": {
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                                "product_name": "Linux",
                                "version": {
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                                            "version_affected": "<",
                                            "version_name": "031ddd280089",
                                            "version_value": "16682588ead4"
                                        },
                                        {
                                            "version_affected": "<",
                                            "version_name": "1c7a387ffef8",
                                            "version_value": "0acce2a5c619"
                                        },
                                        {
                                            "version_value": "not down converted",
                                            "x_cve_json_5_version_data": {
                                                "versions": [
                                                    {
                                                        "version": "6.7",
                                                        "status": "affected"
                                                    },
                                                    {
                                                        "version": "0",
                                                        "lessThan": "6.7",
                                                        "status": "unaffected",
                                                        "versionType": "custom"
                                                    },
                                                    {
                                                        "version": "6.6.37",
                                                        "lessThanOrEqual": "6.6.*",
                                                        "status": "unaffected",
                                                        "versionType": "custom"
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                                                    {
                                                        "version": "6.9.8",
                                                        "lessThanOrEqual": "6.9.*",
                                                        "status": "unaffected",
                                                        "versionType": "custom"
                                                    },
                                                    {
                                                        "version": "6.10",
                                                        "lessThanOrEqual": "*",
                                                        "status": "unaffected",
                                                        "versionType": "original_commit_for_fix"
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    "references": {
        "reference_data": [
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                "url": "https://git.kernel.org/stable/c/16682588ead4a593cf1aebb33b36df4d1e9e4ffa",
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                "name": "https://git.kernel.org/stable/c/0acce2a5c619ef1abdee783d7fea5eac78ce4844"
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