CVE-2026-72086scsi: xen: scsiback: Free the command tag on the TMR submit-failure path

Official description

In the Linux kernel, the following vulnerability has been resolved: scsi: xen: scsiback: Free the command tag on the TMR submit-failure path scsiback_device_action() obtains a command tag in scsiback_get_pend_req() and submits a task-management request with target_submit_tmr(). When target_submit_tmr() fails it returns < 0 and scsiback jumps to the err: label, which sends a response but frees nothing, leaking the tag. Impact: a pvSCSI guest can leak the command tags of a LUN's session, stopping the LUN, by issuing VSCSIIF_ACT_SCSI_ABORT or RESET requests whenever target_submit_tmr() fails. transport_generic_free_cmd() cannot be used here. By the time target_submit_tmr() returns an error it has already run __target_init_cmd() (so se_cmd->cmd_kref is one, not zero), and on its target_get_sess_cmd() error path it has freed se_cmd->se_tmr_req via core_tmr_release_req() while leaving SCF_SCSI_TMR_CDB set and the pointer dangling. Letting the command release run target_free_cmd_mem() would then double-free se_tmr_req. Use the same helper, which returns just the tag, on this path too.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/4567ce79fe2f84c3dcc3a91b22a377cf482d33ad
• https://git.kernel.org/stable/c/6c01f0439098f00a64b246dc27479602201382f7
• https://git.kernel.org/stable/c/18d4f86816592586b38513543b5e1f9553bc271f
• https://git.kernel.org/stable/c/fbc1bdede66d0f2cde83b75d6524ce1a815bb69f
• https://git.kernel.org/stable/c/255fb7b0cdc947b1c01929c7f133281342a3a6b5
• https://git.kernel.org/stable/c/1357fb32d42ad8da193e6da285f09e6452feabda
• https://git.kernel.org/stable/c/66aefc277ebb796ec285d550305535dc3fc0179f