{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2024-39486", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-06-25T14:23:23.747Z", "datePublished": "2024-07-06T09:25:21.514Z", "dateUpdated": "2026-08-05T11:33:38.384Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:33:38.384Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/drm_file: Fix pid refcounting race\n\n, Maxime Ripard\n, Thomas Zimmermann \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, , 1)\n mutex_unlock(&dev->filelist_mutex)\nbegin drm_file_update_pid\nmutex_lock(&dev->filelist_mutex)\nrcu_replace_pointer(filp->pid, , 1)\nmutex_unlock(&dev->filelist_mutex)\nget_pid()\nsynchronize_rcu()\nput_pid() *** pid B reaches refcount 0 and is freed here ***\n get_pid() *** UAF ***\n synchronize_rcu()\n put_pid()\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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The vulnerable code is reached through `ioctl()` on a DRM device node (`/dev/dri/card*` or `/dev/dri/renderD*`), which requires local access to the system. There is no network or remote path into `drm_ioctl_kernel()`.\nAC:L - The attacker owns both sides of the race — `fork()`/SCM_RIGHTS gives two processes sharing one `struct file`, and alternating ioctls from the two tgids re-enter `drm_file_update_pid()`'s update path on demand, so the race can be driven in a tight loop with attacker-controlled CPU pinning and preemption pressure. The required `CONFIG_PREEMPT_RCU` is the default on Android, mainstream distro `PREEMPT_DYNAMIC` kernels, and PREEMPT_RT, so it is not a rare configuration.\nPR:L - Only an unprivileged local user is needed: `drm_file_update_pid()` runs before `drm_ioctl_permit()`, so no DRM_AUTH, DRM_MASTER, or DRM_ROOT_ONLY check applies, and render nodes are routinely accessible to ordinary users (Android apps, desktop `render`/`video` group members) or via a DRM fd passed into a sandbox by the compositor.\nUI:N - The attacker performs the entire sequence itself — open the DRM node, fork, and issue concurrent ioctls. No victim process needs to act or be in any particular state.\nS:U - The use-after-free corrupts kernel slab memory within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed by the flaw itself.\nC:H - The freed `struct pid` can be reallocated with attacker-sprayed data and is subsequently read by `put_pid()` (`pid->numbers[pid->level].ns`) and by pid-lookup paths, giving a use-after-free read primitive that can be leveraged to disclose arbitrary kernel memory.\nI:H - `get_pid()` performs a refcount increment into freed slab memory, and the stale reference later drives `refcount_dec_and_test()` plus `kmem_cache_free()` on a possibly reallocated object — a UAF write and double-free on a core object, which is a well-established primitive for heap grooming and local privilege escalation.\nA:H - The use-after-free on `struct pid` corrupts the pid slab cache and triggers refcount underflow warnings, invalid frees, and kernel oops/panic, and the race can be re-triggered repeatedly by an unprivileged process." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/gpu/drm/drm_file.c" ], "versions": [ { "version": "031ddd28008971cce0b5626379b910d0a05fb4dd", "lessThan": "16682588ead4a593cf1aebb33b36df4d1e9e4ffa", "status": "affected", "versionType": "git" }, { "version": "1c7a387ffef894b1ab3942f0482dac7a6e0a909c", "lessThan": "0acce2a5c619ef1abdee783d7fea5eac78ce4844", "status": "affected", "versionType": "git" }, { "version": "1c7a387ffef894b1ab3942f0482dac7a6e0a909c", "lessThan": "4f2a129b33a2054e62273edd5a051c34c08d96e9", "status": "affected", "versionType": "git" }, { "version": "6.6.9", "lessThan": "6.6.37", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/gpu/drm/drm_file.c" ], "versions": [ { "version": "6.7", "status": "affected" }, { "version": "0", "lessThan": "6.7", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.37", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.9.8", "lessThanOrEqual": "6.9.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.10", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.9", "versionEndExcluding": "6.6.37" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.9.8" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.10" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/16682588ead4a593cf1aebb33b36df4d1e9e4ffa" }, { "url": "https://git.kernel.org/stable/c/0acce2a5c619ef1abdee783d7fea5eac78ce4844" }, { "url": "https://git.kernel.org/stable/c/4f2a129b33a2054e62273edd5a051c34c08d96e9" } ], "title": "drm/drm_file: Fix pid refcounting race", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "timestamp": "2024-07-08T15:13:18.216624Z", "id": "CVE-2024-39486", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "role": "CISA Coordinator", "version": "2.0.3" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2024-07-08T15:13:34.330Z" } }, { "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-02T04:26:15.689Z" }, "title": "CVE Program Container", "references": [ { "url": "https://git.kernel.org/stable/c/16682588ead4a593cf1aebb33b36df4d1e9e4ffa", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/0acce2a5c619ef1abdee783d7fea5eac78ce4844", "tags": [ "x_transferred" ] }, { "url": "https://git.kernel.org/stable/c/4f2a129b33a2054e62273edd5a051c34c08d96e9", "tags": [ "x_transferred" ] } ] } ] } }