{"id":"DEBIAN-CVE-2026-23294","details":"In the Linux kernel, the following vulnerability has been resolved:  bpf: Fix race in devmap on PREEMPT_RT  On PREEMPT_RT kernels, the per-CPU xdp_dev_bulk_queue (bq) can be accessed concurrently by multiple preemptible tasks on the same CPU.  The original code assumes bq_enqueue() and __dev_flush() run atomically with respect to each other on the same CPU, relying on local_bh_disable() to prevent preemption. However, on PREEMPT_RT, local_bh_disable() only calls migrate_disable() (when PREEMPT_RT_NEEDS_BH_LOCK is not set) and does not disable preemption, which allows CFS scheduling to preempt a task during bq_xmit_all(), enabling another task on the same CPU to enter bq_enqueue() and operate on the same per-CPU bq concurrently.  This leads to several races:  1. Double-free / use-after-free on bq-\u003eq[]: bq_xmit_all() snapshots    cnt = bq-\u003ecount, then iterates bq-\u003eq[0..cnt-1] to transmit frames.    If preempted after the snapshot, a second task can call bq_enqueue()    -\u003e bq_xmit_all() on the same bq, transmitting (and freeing) the    same frames. When the first task resumes, it operates on stale    pointers in bq-\u003eq[], causing use-after-free.  2. bq-\u003ecount and bq-\u003eq[] corruption: concurrent bq_enqueue() modifying    bq-\u003ecount and bq-\u003eq[] while bq_xmit_all() is reading them.  3. dev_rx/xdp_prog teardown race: __dev_flush() clears bq-\u003edev_rx and    bq-\u003exdp_prog after bq_xmit_all(). If preempted between    bq_xmit_all() return and bq-\u003edev_rx = NULL, a preempting    bq_enqueue() sees dev_rx still set (non-NULL), skips adding bq to    the flush_list, and enqueues a frame. When __dev_flush() resumes,    it clears dev_rx and removes bq from the flush_list, orphaning the    newly enqueued frame.  4. __list_del_clearprev() on flush_node: similar to the cpumap race,    both tasks can call __list_del_clearprev() on the same flush_node,    the second dereferences the prev pointer already set to NULL.  The race between task A (__dev_flush -\u003e bq_xmit_all) and task B (bq_enqueue -\u003e bq_xmit_all) on the same CPU:    Task A (xdp_do_flush)          Task B (ndo_xdp_xmit redirect)   ----------------------         --------------------------------   __dev_flush(flush_list)     bq_xmit_all(bq)       cnt = bq-\u003ecount  /* e.g. 16 */       /* start iterating bq-\u003eq[] */     \u003c-- CFS preempts Task A --\u003e                                    bq_enqueue(dev, xdpf)                                      bq-\u003ecount == DEV_MAP_BULK_SIZE                                      bq_xmit_all(bq, 0)                                        cnt = bq-\u003ecount  /* same 16! */                                        ndo_xdp_xmit(bq-\u003eq[])                                        /* frames freed by driver */                                        bq-\u003ecount = 0     \u003c-- Task A resumes --\u003e       ndo_xdp_xmit(bq-\u003eq[])       /* use-after-free: frames already freed! */  Fix this by adding a local_lock_t to xdp_dev_bulk_queue and acquiring it in bq_enqueue() and __dev_flush(). These paths already run under local_bh_disable(), so use local_lock_nested_bh() which on non-RT is a pure annotation with no overhead, and on PREEMPT_RT provides a per-CPU sleeping lock that serializes access to the bq.","modified":"2026-09-14T17:02:55.584880985Z","published":"2026-03-25T11:16:24.697Z","upstream":["CVE-2026-23294"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-23294"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.19.8-1"}]}],"versions":["6.12.100-1","6.12.101-1","6.12.105-1","6.12.107-1","6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1","6.12.94-1~bpo12+1","6.12.95-1","6.12.95-1~bpo12+1","6.12.96-1","6.13.10-1~exp1","6.13.11-1~exp1","6.13.2-1~exp1","6.13.3-1~exp1","6.13.4-1~exp1","6.13.5-1~exp1","6.13.6-1~exp1","6.13.7-1~exp1","6.13.8-1~exp1","6.13.9-1~exp1","6.13~rc6-1~exp1","6.13~rc7-1~exp1","6.14.3-1~exp1","6.14.5-1~exp1","6.14.6-1~exp1","6.15-1~exp1","6.15.1-1~exp1","6.15.2-1~exp1","6.15.3-1~exp1","6.15.4-1~exp1","6.15.5-1~exp1","6.15.6-1~exp1","6.15~rc7-1~exp1","6.16-1~exp1","6.16.1-1~exp1","6.16.10-1","6.16.11-1","6.16.12-1","6.16.12-1~bpo13+1","6.16.12-2","6.16.3-1","6.16.3-1~bpo13+1","6.16.5-1","6.16.6-1","6.16.7-1","6.16.8-1","6.16.9-1","6.16~rc7-1~exp1","6.17.10-1","6.17.11-1","6.17.12-1","6.17.13-1","6.17.13-1~bpo13+1","6.17.2-1~exp1","6.17.5-1~exp1","6.17.6-1","6.17.7-1","6.17.7-2","6.17.8-1","6.17.8-1~bpo13+1","6.17.9-1","6.18.1-1~exp1","6.18.10-1","6.18.12-1","6.18.12-1~bpo13+1","6.18.13-1","6.18.14-1","6.18.15-1","6.18.15-1~bpo13+1","6.18.2-1~exp1","6.18.3-1","6.18.5-1","6.18.5-1~bpo13+1","6.18.8-1","6.18.9-1","6.18.9-1~bpo13+1","6.18~rc4-1~exp1","6.18~rc4-1~exp2","6.18~rc5-1~exp1","6.18~rc6-1~exp1","6.18~rc7-1~exp1","6.19-1~exp1","6.19.2-1~exp1","6.19.3-1~exp1","6.19.4-1~exp1","6.19.5-1~exp1","6.19.6-1","6.19.6-2","6.19.6-2~bpo13+1","6.19.8-1~bpo13+1","6.19~rc4-1~exp1","6.19~rc5-1~exp1","6.19~rc6-1~exp1","6.19~rc7-1~exp1","6.19~rc8-1~exp1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-23294.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}