drm/hyperv: validate VMBus packet size in receive callback

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-64527
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-25 10:17:39 UTC
Updated2026-07-25 10:17:39 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: drm/hyperv: validate VMBus packet size in receive callback hyperv_receive_sub() reads msg->vid_hdr.type and dispatches into one of four message-type branches without knowing how many bytes the host wrote into hv->recv_buf. The completion path then runs memcpy(hv->init_buf, msg, VMBUS_MAX_PACKET_SIZE), so the consumer that wakes on wait_for_completion_timeout() can read up to 16 KiB of residue from a prior message as if it were the response payload. Pass bytes_recvd into hyperv_receive_sub() and reject any packet that does not cover the pipe + synthvid header. A single switch on msg->vid_hdr.type then computes the type-specific payload size: the three completion-driving types (SYNTHVID_VERSION_RESPONSE, SYNTHVID_RESOLUTION_RESPONSE, SYNTHVID_VRAM_LOCATION_ACK) fall through to a shared exit that requires that size before memcpy/complete, while SYNTHVID_FEATURE_CHANGE validates its own payload and returns before reading is_dirt_needed. Unknown types are dropped. SYNTHVID_RESOLUTION_RESPONSE is variable length: the host fills resolution_count entries, not the full SYNTHVID_MAX_RESOLUTION_COUNT array. Validate the fixed prefix first so resolution_count can be read, bound it against the array, then require only the count-sized array, so the shorter responses the host actually sends are accepted. Only run the sub-handler when vmbus_recvpacket() returned success. The memcpy length is bytes_recvd, which is bounded by VMBUS_MAX_PACKET_SIZE only on a successful receive; on -ENOBUFS vmbus_recvpacket() instead reports the required length, which can exceed hv->recv_buf, so copying bytes_recvd would read and write past the 16 KiB buffers. Gating on the success return keeps the copy bounded. The nonzero-return path is itself a malformed-message case and is now logged rather than silently skipped; channel recovery is not attempted. Rejected packets are reported via drm_err_ratelimited() rather than silently dropped, matching the CoCo-hardened pattern in hv_kvp_onchannelcallback().

Risk And Classification

EPSS: 0.001610000 probability, percentile 0.056620000 (date 2026-07-29)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 76c56a5affeba1e163b66b9d8cc192e6154466f0 57d5d697642e05d5dd2d40660817765943dd709f git Not specified
CNA Linux Linux affected 76c56a5affeba1e163b66b9d8cc192e6154466f0 f5251226551bfec98c4705641b6f94ff1f238d91 git Not specified
CNA Linux Linux affected 76c56a5affeba1e163b66b9d8cc192e6154466f0 049a6b474823049fe60212f25f26e4b30f44ee8f git Not specified
CNA Linux Linux affected 76c56a5affeba1e163b66b9d8cc192e6154466f0 588c84b461393ff1998ac7b97b04f953f642e0df git Not specified
CNA Linux Linux affected 76c56a5affeba1e163b66b9d8cc192e6154466f0 164dc7bf17609340233c6bf4f66bb7c7008a0511 git Not specified
CNA Linux Linux affected 76c56a5affeba1e163b66b9d8cc192e6154466f0 c8974d96b6a5496f33dc69a3ce28a7bf5078def4 git Not specified
CNA Linux Linux affected 76c56a5affeba1e163b66b9d8cc192e6154466f0 7f87763f47a3c22fb50265a00619ef10f2394b18 git Not specified
CNA Linux Linux affected 5.14 Not specified
CNA Linux Linux unaffected 5.14 semver Not specified
CNA Linux Linux unaffected 5.15.210 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.176 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.143 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.93 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.35 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.12 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/7f87763f47a3c22fb50265a00619ef10f2394b18 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f5251226551bfec98c4705641b6f94ff1f238d91 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/588c84b461393ff1998ac7b97b04f953f642e0df 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/164dc7bf17609340233c6bf4f66bb7c7008a0511 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/049a6b474823049fe60212f25f26e4b30f44ee8f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c8974d96b6a5496f33dc69a3ce28a7bf5078def4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/57d5d697642e05d5dd2d40660817765943dd709f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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