CVE-2026-23342

{"id": "CVE-2026-23342", "cveTags": [], "metrics": {"cvssMetricV31": [{"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 4.7, "attackVector": "LOCAL", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 1.0}]}, "published": "2026-03-25T11:16:32.147", "references": [{"url": "https://git.kernel.org/stable/c/7466ae2aeed483de80c5d8dea0913cf74038b652", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/869c63d5975d55e97f6b168e885452b3da20ea47", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/e67299e1044349ad0088d52c6bc5764cc1816c06", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Primary", "source": "nvd@nist.gov", "description": [{"lang": "en", "value": "CWE-362"}]}], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix race in cpumap on PREEMPT_RT\n\nOn PREEMPT_RT kernels, the per-CPU xdp_bulk_queue (bq) can be accessed\nconcurrently by multiple preemptible tasks on the same CPU.\n\nThe original code assumes bq_enqueue() and __cpu_map_flush() run\natomically with respect to each other on the same CPU, relying on\nlocal_bh_disable() to prevent preemption. However, on PREEMPT_RT,\nlocal_bh_disable() only calls migrate_disable() (when\nPREEMPT_RT_NEEDS_BH_LOCK is not set) and does not disable\npreemption, which allows CFS scheduling to preempt a task during\nbq_flush_to_queue(), enabling another task on the same CPU to enter\nbq_enqueue() and operate on the same per-CPU bq concurrently.\n\nThis leads to several races:\n\n1. Double __list_del_clearprev(): after bq->count is reset in\n bq_flush_to_queue(), a preempting task can call bq_enqueue() ->\n bq_flush_to_queue() on the same bq when bq->count reaches\n CPU_MAP_BULK_SIZE. Both tasks then call __list_del_clearprev()\n on the same bq->flush_node, the second call dereferences the\n prev pointer that was already set to NULL by the first.\n\n2. bq->count and bq->q[] races: concurrent bq_enqueue() can corrupt\n the packet queue while bq_flush_to_queue() is processing it.\n\nThe race between task A (__cpu_map_flush -> bq_flush_to_queue) and\ntask B (bq_enqueue -> bq_flush_to_queue) on the same CPU:\n\n Task A (xdp_do_flush) Task B (cpu_map_enqueue)\n ---------------------- ------------------------\n bq_flush_to_queue(bq)\n spin_lock(&q->producer_lock)\n /* flush bq->q[] to ptr_ring */\n bq->count = 0\n spin_unlock(&q->producer_lock)\n bq_enqueue(rcpu, xdpf)\n <-- CFS preempts Task A --> bq->q[bq->count++] = xdpf\n /* ... more enqueues until full ... */\n bq_flush_to_queue(bq)\n spin_lock(&q->producer_lock)\n /* flush to ptr_ring */\n spin_unlock(&q->producer_lock)\n __list_del_clearprev(flush_node)\n /* sets flush_node.prev = NULL */\n <-- Task A resumes -->\n __list_del_clearprev(flush_node)\n flush_node.prev->next = ...\n /* prev is NULL -> kernel oops */\n\nFix this by adding a local_lock_t to xdp_bulk_queue and acquiring it\nin bq_enqueue() and __cpu_map_flush(). These paths already run under\nlocal_bh_disable(), so use local_lock_nested_bh() which on non-RT is\na pure annotation with no overhead, and on PREEMPT_RT provides a\nper-CPU sleeping lock that serializes access to the bq.\n\nTo reproduce, insert an mdelay(100) between bq->count = 0 and\n__list_del_clearprev() in bq_flush_to_queue(), then run reproducer\nprovided by syzkaller."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nbpf: Corrige condici\u00f3n de carrera en cpumap en PREEMPT_RT\n\nEn kernels PREEMPT_RT, la xdp_bulk_queue (bq) por CPU puede ser accedida concurrentemente por m\u00faltiples tareas preemptibles en la misma CPU.\n\nEl c\u00f3digo original asume que bq_enqueue() y __cpu_map_flush() se ejecutan at\u00f3micamente una con respecto a la otra en la misma CPU, confiando en local_bh_disable() para prevenir la preemption. Sin embargo, en PREEMPT_RT, local_bh_disable() solo llama a migrate_disable() (cuando PREEMPT_RT_NEEDS_BH_LOCK no est\u00e1 configurado) y no deshabilita la preemption, lo que permite que la planificaci\u00f3n CFS preempte una tarea durante bq_flush_to_queue(), permitiendo que otra tarea en la misma CPU entre en bq_enqueue() y opere en la misma bq por CPU concurrentemente.\n\nEsto conduce a varias condiciones de carrera:\n\n1. Doble __list_del_clearprev(): despu\u00e9s de que bq-&gt;count se reinicia en bq_flush_to_queue(), una tarea preemptora puede llamar a bq_enqueue() -&gt; bq_flush_to_queue() en la misma bq cuando bq-&gt;count alcanza CPU_MAP_BULK_SIZE. Ambas tareas luego llaman a __list_del_clearprev() en el mismo bq-&gt;flush_node, la segunda llamada desreferencia el puntero prev que ya hab\u00eda sido establecido a NULL por la primera.\n\n2. Condiciones de carrera de bq-&gt;count y bq-&gt;q[]: bq_enqueue() concurrente puede corromper la cola de paquetes mientras bq_flush_to_queue() la est\u00e1 procesando.\n\nLa condici\u00f3n de carrera entre la tarea A (__cpu_map_flush -&gt; bq_flush_to_queue) y la tarea B (bq_enqueue -&gt; bq_flush_to_queue) en la misma CPU:\n\n Tarea A (xdp_do_flush) Tarea B (cpu_map_enqueue)\n ---------------------- ------------------------\n bq_flush_to_queue(bq)\n spin_lock(&amp;q-&gt;producer_lock)\n /* vaciar bq-&gt;q[] a ptr_ring */\n bq-&gt;count = 0\n spin_unlock(&amp;q-&gt;producer_lock)\n bq_enqueue(rcpu, xdpf)\n &lt;-- CFS preempte la Tarea A --&gt; bq-&gt;q[bq-&gt;count++] = xdpf\n /* ... m\u00e1s encolamientos hasta llenarse ... */\n bq_flush_to_queue(bq)\n spin_lock(&amp;q-&gt;producer_lock)\n /* vaciar a ptr_ring */\n spin_unlock(&amp;q-&gt;producer_lock)\n __list_del_clearprev(flush_node)\n /* establece flush_node.prev = NULL */\n &lt;-- La Tarea A se reanuda --&gt;\n __list_del_clearprev(flush_node)\n flush_node.prev-&gt;next = ...\n /* prev es NULL -&gt; kernel oops */\n\nSolucione esto a\u00f1adiendo un local_lock_t a xdp_bulk_queue y adquiri\u00e9ndolo en bq_enqueue() y __cpu_map_flush(). Estas rutas ya se ejecutan bajo local_bh_disable(), por lo que se usa local_lock_nested_bh() que en sistemas no-RT es una anotaci\u00f3n pura sin sobrecarga, y en PREEMPT_RT proporciona un bloqueo de suspensi\u00f3n por CPU que serializa el acceso a la bq.\n\nPara reproducir, inserte un mdelay(100) entre bq-&gt;count = 0 y __list_del_clearprev() en bq_flush_to_queue(), luego ejecute el reproductor proporcionado por syzkaller."}], "lastModified": "2026-04-23T21:16:19.007", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "07E9D8CD-82F0-4CC6-8038-BF71758D583C", "versionEndExcluding": "6.18.17", "versionStartIncluding": "6.18.1"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "69245D10-0B71-485E-80C3-A64F077004D3", "versionEndExcluding": "6.19.7", "versionStartIncluding": "6.19"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.18:-:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "DCE57113-2223-4308-A0F2-5E6ECFBB3C23"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138"}], "operator": "OR"}]}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}