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    <lastBuildDate>Thu, 01 Oct 2026 16:27:29 +0000</lastBuildDate>
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      <title>CVE-2026-45855 — ata: libata-scsi: avoid Non-NCQ command starvation</title>
      <link>https://vulnerability.circl.lu/vuln/cve-2026-45855</link>
      <description>&lt;p&gt;&lt;strong&gt;Affected:&lt;/strong&gt; Linux&lt;/p&gt;
&lt;p&gt;In the Linux kernel, the following vulnerability has been resolved:&lt;/p&gt;
&lt;p&gt;ata: libata-scsi: avoid Non-NCQ command starvation&lt;/p&gt;
&lt;p&gt;When a non-NCQ command is issued while NCQ commands are being executed,
ata_scsi_qc_issue() indicates to the SCSI layer that the command issuing
should be deferred by returning SCSI_MLQUEUE_XXX_BUSY.  This command
deferring is correct and as mandated by the ACS specifications since
NCQ and non-NCQ commands cannot be mixed.&lt;/p&gt;
&lt;p&gt;However, in the case of a host adapter using multiple submission queues,
when the target device is under a constant load of NCQ commands, there
are no guarantees that requeueing the non-NCQ command will be executed
later and it may be deferred again repeatedly as other submission queues
can constantly issue NCQ commands from different CPUs ahead of the
non-NCQ command. This can lead to very long delays for the execution of
non-NCQ commands, and even complete starvation for these commands in the
worst case scenario.&lt;/p&gt;
&lt;p&gt;Since the block layer and the SCSI layer do not distinguish between
queueable (NCQ) and non queueable (non-NCQ) commands, libata-scsi SAT
implementation must ensure forward progress for non-NCQ commands in the
presence of NCQ command traffic. This is similar to what SAS HBAs with a
hardware/firmware based SAT implementation do.&lt;/p&gt;
&lt;p&gt;Implement such forward progress guarantee by limiting requeueing of
non-NCQ commands from ata_scsi_qc_issue(): when a non-NCQ command is
received and NCQ commands are in-flight, do not force a requeu…&lt;/p&gt;</description>
      <content:encoded>&lt;p&gt;&lt;strong&gt;Affected:&lt;/strong&gt; Linux&lt;/p&gt;
&lt;p&gt;In the Linux kernel, the following vulnerability has been resolved:&lt;/p&gt;
&lt;p&gt;ata: libata-scsi: avoid Non-NCQ command starvation&lt;/p&gt;
&lt;p&gt;When a non-NCQ command is issued while NCQ commands are being executed,
ata_scsi_qc_issue() indicates to the SCSI layer that the command issuing
should be deferred by returning SCSI_MLQUEUE_XXX_BUSY.  This command
deferring is correct and as mandated by the ACS specifications since
NCQ and non-NCQ commands cannot be mixed.&lt;/p&gt;
&lt;p&gt;However, in the case of a host adapter using multiple submission queues,
when the target device is under a constant load of NCQ commands, there
are no guarantees that requeueing the non-NCQ command will be executed
later and it may be deferred again repeatedly as other submission queues
can constantly issue NCQ commands from different CPUs ahead of the
non-NCQ command. This can lead to very long delays for the execution of
non-NCQ commands, and even complete starvation for these commands in the
worst case scenario.&lt;/p&gt;
&lt;p&gt;Since the block layer and the SCSI layer do not distinguish between
queueable (NCQ) and non queueable (non-NCQ) commands, libata-scsi SAT
implementation must ensure forward progress for non-NCQ commands in the
presence of NCQ command traffic. This is similar to what SAS HBAs with a
hardware/firmware based SAT implementation do.&lt;/p&gt;
&lt;p&gt;Implement such forward progress guarantee by limiting requeueing of
non-NCQ commands from ata_scsi_qc_issue(): when a non-NCQ command is
received and NCQ commands are in-flight, do not force a requeu…&lt;/p&gt;</content:encoded>
      <guid isPermaLink="false">https://vulnerability.circl.lu/vuln/cve-2026-45855</guid>
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