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CVE-2026-72085

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

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, and 1 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 2dbcdf33dbf61f44b29adb52338282c3d7840d0e · fixed in 9c0f6894982b1f13bda220707497b25ac9c95bdb; From 2dbcdf33dbf61f44b29adb52338282c3d7840d0e · fixed in a13b789497a7fdd27d4d63f5c69d23db706ef0fe; From 2dbcdf33dbf61f44b29adb52338282c3d7840d0e · fixed in fa588f28401102652068c4cc75e135507f4b5106; From 2dbcdf33dbf61f44b29adb52338282c3d7840d0e · fixed in fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45; From 2dbcdf33dbf61f44b29adb52338282c3d7840d0e · fixed in f1516c56ac540da1769f264c3cfefe4499548a5d; From 2dbcdf33dbf61f44b29adb52338282c3d7840d0e · fixed in 1e97c404e44991fb087c38ccd7414f2d326f9b74; From 2dbcdf33dbf61f44b29adb52338282c3d7840d0e · fixed in ca978f8a93d4d36841839bf2847d29b88c2591d6

  • Linux Linux

    4.6

  • KernelLinux

    From 4.6.0 · fixed in 5.15.212; From 5.16.0 · fixed in 6.1.178; From 6.2.0 · fixed in 6.6.145; From 6.7.0 · fixed in 6.12.97; From 6.13.0 · fixed in 6.18.40; From 6.19.0 · fixed in 7.1.5

References 7

git.kernel.org