Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-05-01T00:00:00 kernel: scsi: target: tcm_loop: Drain commands in target_reset handler 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CWE-772

In the Linux kernel, the following vulnerability has been resolved: scsi: target: tcm_loop: Drain commands in target_reset handler tcm_loop_target_reset() violates the SCSI EH contract: it returns SUCCESS without draining any in-flight commands. The SCSI EH documentation (scsi_eh.rst) requires that when a reset handler returns SUCCESS the driver has made lower layers "forget about timed out scmds" and is ready for new commands. Every other SCSI LLD (virtio_scsi, mpt3sas, ipr, scsi_debug, mpi3mr) enforces this by draining or completing outstanding commands before returning SUCCESS. Because tcm_loop_target_reset() doesn't drain, the SCSI EH reuses in-flight scsi_cmnd structures for recovery commands (e.g. TUR) while the target core still has async completion work queued for the old se_cmd. The memset in queuecommand zeroes se_lun and lun_ref_active, causing transport_lun_remove_cmd() to skip its percpu_ref_put(). The leaked LUN reference prevents transport_clear_lun_ref() from completing, hanging configfs LUN unlink forever in D-state: INFO: task rm:264 blocked for more than 122 seconds. rm D 0 264 258 0x00004000 Call Trace: __schedule+0x3d0/0x8e0 schedule+0x36/0xf0 transport_clear_lun_ref+0x78/0x90 [target_core_mod] core_tpg_remove_lun+0x28/0xb0 [target_core_mod] target_fabric_port_unlink+0x50/0x60 [target_core_mod] configfs_unlink+0x156/0x1f0 [configfs] vfs_unlink+0x109/0x290 do_unlinkat+0x1d5/0x2d0 Fix this by making tcm_loop_target_reset() actually drain commands: 1. Issue TMR_LUN_RESET via tcm_loop_issue_tmr() to drain all commands that the target core knows about (those not yet CMD_T_COMPLETE). 2. Use blk_mq_tagset_busy_iter() to iterate all started requests and flush_work() on each se_cmd — this drains any deferred completion work for commands that already had CMD_T_COMPLETE set before the TMR (which the TMR skips via __target_check_io_state()). This is the same pattern used by mpi3mr, scsi_debug, and libsas to drain outstanding commands during reset.

A flaw was found in the Linux kernel's SCSI target subsystem, specifically within the `tcm_loop` module. This vulnerability arises when the `tcm_loop_target_reset()` function, responsible for handling target resets, fails to properly clear out commands that are still being processed. A local user or process could exploit this by initiating a target reset, which leads to unreleased resource references for Logical Unit Numbers (LUNs). The primary consequence is a Denial of Service (DoS) condition, where the system may become unresponsive when attempting to remove a LUN.

tcm_loop target reset must drain in-flight commands before reporting success to SCSI EH; otherwise completions race recovery and leak LUN refs, hanging configfs unlink. Red Hat advises LIO/tcm_loop users to patch target-mode kernels. Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Out of support scope kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Fix deferred kernel Red Hat Enterprise Linux 8 Fix deferred kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-43054 https://nvd.nist.gov/vuln/detail/CVE-2026-43054 https://lore.kernel.org/linux-cve-announce/2026050107-CVE-2026-43054-95b4@gregkh/T