{"id":"CVE-2026-97992","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nvhost-vdpa: protect config_ctx from being freed under the config callback\n\nvhost_vdpa_config_cb() loads v->config_ctx and signals it without taking\na reference and with…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nvhost-vdpa: protect config_ctx from being freed under the config callback\n\nvhost_vdpa_config_cb() loads v->config_ctx and signals it without taking\na reference and with…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 776f395004d829bbbf18c159ed9beb517a208c71 < bf35c8948ab7a3eaf1f724fa1e870e3f73a1749b","Linux >= 776f395004d829bbbf18c159ed9beb517a208c71 < 5a075ee2398929d5cc1393666f219c35332becb1","Linux >= 776f395004d829bbbf18c159ed9beb517a208c71 < f4a93f15ed1c8406ba5c8e5b28cafacb2b3bcd11","Linux >= 776f395004d829bbbf18c159ed9beb517a208c71 < 62be4e3e5f5f947fbf765b914cebdc478f715d12","Linux 5.8"],"published":"2026-09-25","updated":"2026-09-25","sourceUpdated":"2026-09-25T11:17:27.343","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-97992","references":[{"url":"https://git.kernel.org/stable/c/5a075ee2398929d5cc1393666f219c35332becb1","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/62be4e3e5f5f947fbf765b914cebdc478f715d12","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/bf35c8948ab7a3eaf1f724fa1e870e3f73a1749b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f4a93f15ed1c8406ba5c8e5b28cafacb2b3bcd11","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-09-25T11:06:38.865Z","slug":"CVE-2026-97992","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nvhost-vdpa: protect config_ctx from being freed under the config callback\n\nvhost_vdpa_config_cb() loads v->config_ctx and signals it without taking\na reference and without holding any lock:\n\n\tstruct eventfd_ctx *config_ctx = v->config_ctx;\n\n\tif (config_ctx)\n\t\teventfd_signal(config_ctx);\n\nVHOST_VDPA_SET_CONFIG_CALL replaces that field and drops what is normally\nthe last reference to the old context:\n\n\tswap(ctx, v->config_ctx);\n\n\tif (ctx)\n\t\teventfd_ctx_put(ctx);\n\neventfd_ctx_put() drops the last kref and frees the context immediately,\nwith no RCU grace period, so a callback that has already loaded the\npointer goes on to dereference freed memory.  The two sides share no\nlock: the ioctl runs under vhost_dev.mutex, while the parent invokes the\ncallback from its own interrupt or workqueue context.\n\nThis is not the reopen refcount underflow fixed by commit f6bbf0010ba0\n(\"vhost-vdpa: fix use-after-free of v->config_ctx\"), which was about\nvhost_vdpa_config_put() leaving a stale pointer behind.  Here the pointer\nis maintained correctly and it is the read side that is unprotected.\n\nWith VDUSE as the parent this is reachable from userspace with access to\n/dev/vduse (root by default).  VDUSE_DEV_INJECT_CONFIG_IRQ queues\ndev->inject, and vduse_dev_irq_inject() runs the callback under VDUSE's\nown dev->irq_lock, which vhost does not hold.  vduse_dev_reset() does\nflush_work(&dev->inject), but VHOST_VDPA_SET_CONFIG_CALL never goes\nthrough reset, so an inject already in flight is not waited for.  A\nprocess that injects config interrupts on the VDUSE fd while another\nthread swaps the call fd on the vhost-vdpa fd hits it in seconds:\n\n  BUG: KASAN: slab-use-after-free in native_queued_spin_lock_slowpath\n  Read of size 4 at addr ffff888107d21808 by task kworker/u17:1/2993\n  Workqueue: vduse-irq vduse_dev_irq_inject\n  Call Trace:\n   native_queued_spin_lock_slowpath+0x97/0x5b0\n   _raw_spin_lock_irqsave+0xd4/0xe0\n   eventfd_signal_mask+0x69/0x120\n   vhost_vdpa_config_cb+0x34/0x50\n   vduse_dev_irq_inject+0x46/0x60\n   process_one_work+0x468/0x950\n\n  Allocated by task 2992:\n   do_eventfd+0x50/0x200\n   __x64_sys_eventfd2+0x2e/0x40\n\n  Freed by task 2992:\n   eventfd_ctx_put+0xb9/0xc0\n   vhost_vdpa_unlocked_ioctl+0x116c/0x2190\n\nAdd a spinlock covering every access to config_ctx, so the callback\neither signals a context that is still alive or observes NULL, and the\nput happens only once no callback can reach the old value.\n\nClearing the parent's callback before the put would not be enough: of the\nin-tree set_config_cb() implementations only VDUSE takes a lock, the rest\nstore the pointer unlocked, so that would not order against an in-flight\ninvocation.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}