scsi: xen: scsiback: Free unsubmitted command instead of double-putting it
In 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.
CVE-2026-72085
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-72085
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2dbcdf33dbf61f44b29adb52338282c3d7840d0e",
"lessThan": "9c0f6894982b1f13bda220707497b25ac9c95bdb",
"versionType": "git"
},
{
"status": "affected",
"version": "2dbcdf33dbf61f44b29adb52338282c3d7840d0e",
"lessThan": "a13b789497a7fdd27d4d63f5c69d23db706ef0fe",
"versionType": "git"
},
{
"status": "affected",
"version": "2dbcdf33dbf61f44b29adb52338282c3d7840d0e",
"lessThan": "fa588f28401102652068c4cc75e135507f4b5106",
"versionType": "git"
},
{
"status": "affected",
"version": "2dbcdf33dbf61f44b29adb52338282c3d7840d0e",
"lessThan": "fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45",
"versionType": "git"
},
{
"status": "affected",
"version": "2dbcdf33dbf61f44b29adb52338282c3d7840d0e",
"lessThan": "f1516c56ac540da1769f264c3cfefe4499548a5d",
"versionType": "git"
},
{
"status": "affected",
"version": "2dbcdf33dbf61f44b29adb52338282c3d7840d0e",
"lessThan": "1e97c404e44991fb087c38ccd7414f2d326f9b74",
"versionType": "git"
},
{
"status": "affected",
"version": "2dbcdf33dbf61f44b29adb52338282c3d7840d0e",
"lessThan": "ca978f8a93d4d36841839bf2847d29b88c2591d6",
"versionType": "git"
}
],
"programFiles": [
"drivers/xen/xen-scsiback.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.6"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.6",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.15.212",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.178",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.145",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.97",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.40",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.5",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"drivers/xen/xen-scsiback.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-72085
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #41864 · Revision 1
- Added to Heist Feed
- Publisher date