CVE-2026-45855
published 2026-05-27CVE-2026-45855: In the Linux kernel, the following vulnerability has been resolved: ata: libata-scsi: avoid Non-NCQ command starvation When a non-NCQ command is issued while…
medium5.5
In the Linux kernel, the following vulnerability has been resolved:
ata: libata-scsi: avoid Non-NCQ command starvation
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.
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.
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.
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 requeue of the
non-NCQ command by returning SCSI_MLQUEUE_XXX_BUSY and instead return 0
to indicate that the command was accepted but hold on to the qc using
the new deferred_qc field of struct ata_port.
This deferred qc will be issued using the work item deferred_qc_work
running the function ata_scsi_deferred_qc_work() once all in-flight
commands complete, which is checked with the port qc_defer() callback
return value indicating that no further delay is necessary. This check
is done using the helper f
Affected
6 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| linux | linux | — | — |
| linux | linux | >= bdb01301f3ea51a59eff252b06643fc1fe843e57 < ce22aaed011206fed9cbd8c9c2d44718607f31ee | ce22aaed011206fed9cbd8c9c2d44718607f31ee |
| linux | linux | >= bdb01301f3ea51a59eff252b06643fc1fe843e57 < 888cd7e40adb2ef4af1b4d3b6e2e83ad409ae8c2 | 888cd7e40adb2ef4af1b4d3b6e2e83ad409ae8c2 |
| linux | linux | >= bdb01301f3ea51a59eff252b06643fc1fe843e57 < 5d61a38a60e62750526d94663b69b7ac5c7f07a5 | 5d61a38a60e62750526d94663b69b7ac5c7f07a5 |
| linux | linux | >= bdb01301f3ea51a59eff252b06643fc1fe843e57 < 0ea84089dbf62a92dc7889c79e6b18fc89260808 | 0ea84089dbf62a92dc7889c79e6b18fc89260808 |
| linux | linux_kernel | — | — |