scsi: xen: scsiback: Free unsubmitted command instead of double-putting it

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-72085
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 06:21:22 UTC
Updated2026-08-15 06:21:22 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: scsi: xen: scsiback: Free unsubmitted command instead of double-putting it scsiback_get_pend_req() obtains a command tag and returns a vscsibk_pend whose embedded se_cmd has only been memset to 0, so its cmd_kref is 0; the se_cmd is initialised (kref_init() via target_init_cmd()) only later, in scsiback_cmd_exec(), on the successful VSCSIIF_ACT_SCSI_CDB path. The two error paths in scsiback_do_cmd_fn() taken before the command is submitted -- a failed scsiback_gnttab_data_map() and an unknown ring_req.act -- call transport_generic_free_cmd(&pending_req->se_cmd, 0), which kref_put()s a refcount of 0. That underflows it ("refcount_t: underflow; use-after-free") and, as the release function is not run, leaks the command tag. Impact: a pvSCSI guest can leak every command tag of a LUN's session, stopping the LUN, by submitting requests with a bad grant reference or an unknown request type; under panic_on_warn the refcount underflow panics the host. Add a helper that just returns the tag with target_free_tag() and sends the error response. It frees the tag while the v2p reference still pins the session, and snapshots the response fields beforehand because freeing the tag can let another ring reuse the pending_req slot.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 2dbcdf33dbf61f44b29adb52338282c3d7840d0e 9c0f6894982b1f13bda220707497b25ac9c95bdb git Not specified
CNA Linux Linux affected 2dbcdf33dbf61f44b29adb52338282c3d7840d0e a13b789497a7fdd27d4d63f5c69d23db706ef0fe git Not specified
CNA Linux Linux affected 2dbcdf33dbf61f44b29adb52338282c3d7840d0e fa588f28401102652068c4cc75e135507f4b5106 git Not specified
CNA Linux Linux affected 2dbcdf33dbf61f44b29adb52338282c3d7840d0e fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45 git Not specified
CNA Linux Linux affected 2dbcdf33dbf61f44b29adb52338282c3d7840d0e f1516c56ac540da1769f264c3cfefe4499548a5d git Not specified
CNA Linux Linux affected 2dbcdf33dbf61f44b29adb52338282c3d7840d0e 1e97c404e44991fb087c38ccd7414f2d326f9b74 git Not specified
CNA Linux Linux affected 2dbcdf33dbf61f44b29adb52338282c3d7840d0e ca978f8a93d4d36841839bf2847d29b88c2591d6 git Not specified
CNA Linux Linux affected 4.6 Not specified
CNA Linux Linux unaffected 4.6 semver Not specified
CNA Linux Linux unaffected 5.15.212 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.178 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.145 6.6.* 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-rc4 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/1e97c404e44991fb087c38ccd7414f2d326f9b74 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fa588f28401102652068c4cc75e135507f4b5106 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a13b789497a7fdd27d4d63f5c69d23db706ef0fe 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9c0f6894982b1f13bda220707497b25ac9c95bdb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f1516c56ac540da1769f264c3cfefe4499548a5d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ca978f8a93d4d36841839bf2847d29b88c2591d6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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