scsi: xen: scsiback: Free unsubmitted command instead of double-putting it
Published Aug 15, 2026
9.3
CRITICALCVSS 3.1
EPSS 0.19%
Description
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.
Affected products
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- Version StatusaffectedConstraints
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- Version
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- Version 4.6StatusaffectedConstraints-
- Version 0StatusunaffectedConstraints<4.6
- Version 5.15.212StatusunaffectedConstraints<=5.15.*
- Version 6.1.178StatusunaffectedConstraints<=6.1.*
- Version 6.12.97StatusunaffectedConstraints<=6.12.*
- Version 6.18.40StatusunaffectedConstraints<=6.18.*
- Version 6.6.145StatusunaffectedConstraints<=6.6.*
- Version 7.1.5StatusunaffectedConstraints<=7.1.*
- Version 7.2StatusunaffectedConstraints<=*
- Version
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
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| Linux | Linux | affected |
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No data.
No data.
Red Hat Enterprise Linux 10
kernel
Not affected
Red Hat Enterprise Linux 6
kernel
Not affected
Red Hat Enterprise Linux 7
kernel
Not affected
Red Hat Enterprise Linux 7
kernel-rt
Not affected
Red Hat Enterprise Linux 8
kernel
Not affected
Red Hat Enterprise Linux 8
kernel-rt
Not affected
Red Hat Enterprise Linux 9
kernel
Not affected
Red Hat Enterprise Linux 9
kernel-rt
Not affected
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 6 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | n/a |
| Red Hat Enterprise Linux 8 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | n/a |
| Red Hat Enterprise Linux 9 | kernel | Not affected | n/a |
| Red Hat Enterprise Linux 9 | kernel-rt | Not affected | n/a |
No package ranges for this CVE.
Remediation
No remediation recorded yet.
References (12)
- https://access.redhat.com/security/cve/CVE-2026-72085 Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2516535 Issue Tracking
- https://git.kernel.org/stable/c/1e97c404e44991fb087c38ccd7414f2d326f9b74
- https://git.kernel.org/stable/c/9c0f6894982b1f13bda220707497b25ac9c95bdb
- https://git.kernel.org/stable/c/a13b789497a7fdd27d4d63f5c69d23db706ef0fe
- https://git.kernel.org/stable/c/ca978f8a93d4d36841839bf2847d29b88c2591d6
- https://git.kernel.org/stable/c/f1516c56ac540da1769f264c3cfefe4499548a5d
- https://git.kernel.org/stable/c/fa588f28401102652068c4cc75e135507f4b5106
- https://git.kernel.org/stable/c/fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45
- https://lore.kernel.org/linux-cve-announce/2026081521-CVE-2026-72085-3058@gregkh/T
- https://nvd.nist.gov/vuln/detail/CVE-2026-72085
- https://www.cve.org/CVERecord?id=CVE-2026-72085
Change history (0)
No recorded changes yet.