vhost: fix vhost_get_avail_idx for a non empty ring

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74356
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 06:22:37 UTC
Updated2026-08-15 06:22:37 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: vhost: fix vhost_get_avail_idx for a non empty ring vhost_get_avail_idx is supposed to report whether it has updated vq->avail_idx. Instead, it returns whether all entries have been consumed, which is usually the same. But not always - in drivers/vhost/net.c and when mergeable buffers have been enabled, the driver checks whether the combined entries are big enough to store an incoming packet. If not, the driver re-enables notifications with available entries still in the ring. The incorrect return value from vhost_get_avail_idx propagates through vhost_enable_notify and causes the host to livelock if the guest is not making progress, as vhost will immediately disable notifications and retry using the available entries. This goes back to commit d3bb267bbdcb ("vhost: cache avail index in vhost_enable_notify()") which changed vhost_enable_notify() to compare the freshly read avail index against vq->last_avail_idx instead of the previously cached vq->avail_idx. Commit 7ad472397667 ("vhost: move smp_rmb() into vhost_get_avail_idx()") then carried over the same comparison when refactoring vhost_enable_notify() to call the unified vhost_get_avail_idx(). The obvious fix is to make vhost_get_avail_idx do what the comment says it does and report whether new entries have been added.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected d3bb267bbdcba199568f1325743d9d501dea0560 e115471008111f894c6528d9ab2ce7d0ce306f35 git Not specified
CNA Linux Linux affected d3bb267bbdcba199568f1325743d9d501dea0560 7f229d27bf27c7e589eca690d8612763a7a4801f git Not specified
CNA Linux Linux affected d3bb267bbdcba199568f1325743d9d501dea0560 a9326b652bc7acd748d7a1143573845c7924d847 git Not specified
CNA Linux Linux affected d3bb267bbdcba199568f1325743d9d501dea0560 09861858a68342f851f71c669ac0f69865c32151 git Not specified
CNA Linux Linux affected 5.18 Not specified
CNA Linux Linux unaffected 5.18 semver Not specified
CNA Linux Linux unaffected 6.12.97 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.40 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.5 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a9326b652bc7acd748d7a1143573845c7924d847 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7f229d27bf27c7e589eca690d8612763a7a4801f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e115471008111f894c6528d9ab2ce7d0ce306f35 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/09861858a68342f851f71c669ac0f69865c32151 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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