kernel/linux.git/drivers/ata/libata-scsi.c, branch v6.12.98

ata: libata-scsi: limit simulated SCSI command copy to response length

2026-07-24T14:11:22+00:00

[ Upstream commit cd64be0ecd399fa2b1ab60b3aaf2b2b744243467 ] The function ata_scsi_rbuf_fill() is used to copy the response of emulated SCSI commands from ata_scsi_rbuf to the SCSI command's scatterlist. Currently, sg_copy_from_buffer() is called with the size argument set to ATA_SCSI_RBUF_SIZE (2048 bytes). Since ata_scsi_rbuf is zeroed out before the simulation actor is invoked, copying the full buffer size causes the remainder of the SCSI command's transfer buffer (beyond the actual response length 'len') to be overwritten with zeroes. This clobbers any pre-existing sentinel values or data in the caller's buffer tail, even though the correct residual count is reported via scsi_set_resid(). Fix this by passing the actual response length 'len' as the copy size to sg_copy_from_buffer(), ensuring that the tail of the caller's buffer remains untouched. Also, add a defensive check to ensure that the actor does not return a length exceeding the static buffer capacity. If this occurs, trigger a WARN_ON(), fail the command with an aborted command error, and return immediately without copying any data. The fix was tested by invoking an SCSI SG_IO INQUIRY on an ATA disk on vanilla build, and build with the fix. Confirmed that the input buffer's tail end remains unmodified with the fix. Fixes: 5251ae224d8d ("ata: libata-scsi: Return residual for emulated SCSI commands") Assisted-by: Antigravity:gemini-3.5-flash Signed-off-by: Karuna Ramkumar Signed-off-by: Damien Le Moal Signed-off-by: Sasha Levin

ata: libata-scsi: do not needlessly defer commands when using PMP with FBS

2026-06-01T15:46:15+00:00

commit 759e8756da00aa115d504a18155b1d1ee1cc12e8 upstream. The ACS specification does not allow a non-NCQ command to be issued while an NCQ command is outstanding. Commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") introduced a feature where a deferred non-NCQ command gets issued from a workqueue. The design stores a single non-NCQ command per port. However, when using Port Multipliers (PMPs), specifically PMPs that support FIS-Based Switching (FBS), non-NCQ and NCQ commands can be mixed on the same port, just not for the same link, see e.g. ata_std_qc_defer() which is, and always has operated on a per-link basis. Therefore, move the deferred_qc from struct ata_port to struct ata_link. This way, when using a PMP with FBS, we will not needlessly defer commands to all other links, just because one link issued a non-NCQ command while having an NCQ command outstanding. Only commands for that specific link will be deferred. This is in line with how PMPs with FBS worked before commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation"). Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") Tested-by: Tommy Kelly Reviewed-by: Damien Le Moal Signed-off-by: Niklas Cassel Signed-off-by: Greg Kroah-Hartman

ata: libata-scsi: do not use the deferred QC feature on PMPs with CBS

2026-06-01T15:46:15+00:00

commit f233124fb36cd57ef09f96d517a38ab4b902e15e upstream. When using Port Multipliers (PMPs) with Command-Based Switching (CBS), you can only issue commands to one link at a time. For PMPs with CBS, there is already code to handle commands being sent to different links in sata_pmp_qc_defer_cmd_switch() using ap->excl_link. sata_sil24 also makes use of ap->excl_link. A user on the list reported that commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") broke PMPs with CBS. The commit introduced code that stores a deferred qc in ap->deferred_qc, to later be issued via a workqueue. It turns out that this change is incompatible with the existing ap->excl_link handling used by PMPs with CBS. Thus, modify sata_pmp_qc_defer_cmd_switch() and sil24_qc_defer() to return ATA_DEFER_LINK_EXCL, and make sure that the deferred QC handling via workqueue is not used for this return value. This way, PMPs with CBS will work once again. Note that the starvation referenced in commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") can only happen on libsas ports, and libsas does not support Port Multipliers, thus there is no harm of reverting back to the previous way of deferring commands for PMPs with CBS. Non-libsas ports connected to anything but a PMP with CBS (e.g. a normal drive or a PMP with FBS) will continue using the deferred workqueue, since it does result in lower completion latencies for non-NCQ commands, even though the workqueue is not strictly needed to avoid starvation for non-libsas ports. If we want to modify the scope of the workqueue issuing to also handle PMPs with CBS, then we should ensure that we can save both NCQ and non-NCQ commands in ap->deferred_qc, while also removing the existing PMP CBS handling using ap->excl_link, such that we don't duplicate features. While at it, also add a comment explaining how the ap->excl_link mechanism works. Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") Tested-by: Tommy Kelly Reported-by: Tommy Kelly Closes: https://lore.kernel.org/linux-ide/ce09cc21-a8e9-4845-b205-35411e22fba9@tkel.ly/ Reviewed-by: Damien Le Moal Signed-off-by: Niklas Cassel Signed-off-by: Greg Kroah-Hartman

ata: libata-scsi: do not use the deferred QC feature for ATA_DEFER_PORT

2026-06-01T15:46:15+00:00

commit ce4548807d2e4ae48fd0dbe38865467369877913 upstream. The deferred QC feature was meant to handle mixed NCQ and non-NCQ commands, i.e. for return value ATA_DEFER_LINK. ATA_DEFER_PORT is returned by PATA drivers, but also certain SATA drivers like sata_mv and sata_sil24 that uses ap->excl_link to workaround hardware bugs in these HBAs. Regardless of the reason, using the deferred QC feature for ATA_DEFER_PORT is always wrong, and will break the ap->excl_link usage of the SATA drivers that rely on that feature. Modify ata_scsi_qc_issue() to only use the deferred QC feature when mixing NCQ and non-NCQ commands, i.e. ATA_DEFER_LINK. Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") Tested-by: Tommy Kelly Reviewed-by: Damien Le Moal Signed-off-by: Niklas Cassel Signed-off-by: Greg Kroah-Hartman

ata: libata-scsi: improve readability of ata_scsi_qc_issue()

2026-06-01T15:46:15+00:00

commit 360190bd965f93794d5f5685a6de22ce6da2b672 upstream. Improve readability of ata_scsi_qc_issue(). No functional changes. Tested-by: Tommy Kelly Reviewed-by: Damien Le Moal Signed-off-by: Niklas Cassel Signed-off-by: Greg Kroah-Hartman

ata: libata-scsi: fix requeue of deferred ATA PASS-THROUGH commands

2026-05-23T11:04:59+00:00

[ Upstream commit 8ebf408e7d463eee02c348a3c8277b95587b710d ] Commit 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") introduced ata_scsi_requeue_deferred_qc() to handle commands deferred during resets or NCQ failures. This deferral logic completed commands with DID_SOFT_ERROR to trigger a retry in the SCSI mid-layer. However, DID_SOFT_ERROR is subject to scsi_cmd_retry_allowed() checks. ATA PASS-THROUGH commands sent via SG_IO ioctl have scmd->allowed set to zero. This causes the mid-layer to fail the command immediately instead of retrying, even though the command was never actually issued to the hardware. Switch to DID_REQUEUE to ensure these commands are inserted back into the request queue regardless of retry limits. Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") Reviewed-by: Damien Le Moal Signed-off-by: Igor Pylypiv Signed-off-by: Niklas Cassel Signed-off-by: Sasha Levin

ata: libata-scsi: report correct sense field pointer in ata_scsiop_maint_in()

2026-03-25T10:08:50+00:00

[ Upstream commit e6d7eba23b666d85cacee0643be280d6ce1ebffc ] Commit 4ab7bb976343 ("ata: libata-scsi: Refactor ata_scsiop_maint_in()") modified ata_scsiop_maint_in() to directly call ata_scsi_set_invalid_field() to set the field pointer of the sense data of a failed MAINTENANCE IN command. However, in the case of an invalid command format, the sense data field incorrectly indicates byte 1 of the CDB. Fix this to indicate byte 2 of the command. Reported-by: Guenter Roeck Fixes: 4ab7bb976343 ("ata: libata-scsi: Refactor ata_scsiop_maint_in()") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal Signed-off-by: Niklas Cassel Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

ata: libata-scsi: Return residual for emulated SCSI commands

2026-03-25T10:08:50+00:00

[ Upstream commit 5251ae224d8d3caa21b28d12408062b6e75cffad ] The function ata_scsi_rbuf_fill() used to fill the reply buffer of emulated SCSI commands always copies the ATA reply buffer (ata_scsi_rbuf) up to the size of the SCSI command buffer (the transfer length for the command), even if the reply is shorter than the SCSI command buffer. This leads to issuers of the SCSI command to always get a result without any residual (resid is always 0) despite the potentially shorter reply for the command. Modify all fill actors used by ata_scsi_rbuf_fill() to return the number of bytes filled for the reply and 0 in case of error. Using this value, add a call to scsi_set_resid() in ata_scsi_rbuf_fill() to set the correct residual for the SCSI command when the reply length is shorter than the command buffer. Signed-off-by: Damien Le Moal Link: https://lore.kernel.org/r/20241022024537.251905-7-dlemoal@kernel.org Signed-off-by: Niklas Cassel Stable-dep-of: e6d7eba23b66 ("ata: libata-scsi: report correct sense field pointer in ata_scsiop_maint_in()") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

ata: libata: cancel pending work after clearing deferred_qc

2026-03-13T16:20:49+00:00

commit aac9b27f7c1f2b2cf7f50a9ca633ecbbcaf22af9 upstream. Syzbot reported a WARN_ON() in ata_scsi_deferred_qc_work(), caused by ap->ops->qc_defer() returning non-zero before issuing the deferred qc. ata_scsi_schedule_deferred_qc() is called during each command completion. This function will check if there is a deferred QC, and if ap->ops->qc_defer() returns zero, meaning that it is possible to queue the deferred qc at this time (without being deferred), then it will queue the work which will issue the deferred qc. Once the work get to run, which can potentially be a very long time after the work was scheduled, there is a WARN_ON() if ap->ops->qc_defer() returns non-zero. While we hold the ap->lock both when assigning and clearing deferred_qc, and the work itself holds the ap->lock, the code currently does not cancel the work after clearing the deferred qc. This means that the following scenario can happen: 1) One or several NCQ commands are queued. 2) A non-NCQ command is queued, gets stored in ap->deferred_qc. 3) Last NCQ command gets completed, work is queued to issue the deferred qc. 4) Timeout or error happens, ap->deferred_qc is cleared. The queued work is currently NOT canceled. 5) Port is reset. 6) One or several NCQ commands are queued. 7) A non-NCQ command is queued, gets stored in ap->deferred_qc. 8) Work is finally run. Yet at this time, there is still NCQ commands in flight. The work in 8) really belongs to the non-NCQ command in 2), not to the non-NCQ command in 7). The reason why the work is executed when it is not supposed to, is because it was never canceled when ap->deferred_qc was cleared in 4). Thus, ensure that we always cancel the work after clearing ap->deferred_qc. Another potential fix would have been to let ata_scsi_deferred_qc_work() do nothing if ap->ops->qc_defer() returns non-zero. However, canceling the work when clearing ap->deferred_qc seems slightly more logical, as we hold the ap->lock when clearing ap->deferred_qc, so we know that the work cannot be holding the lock. (The function could be waiting for the lock, but that is okay since it will do nothing if ap->deferred_qc is not set.) Reported-by: syzbot+bcaf842a1e8ead8dfb89@syzkaller.appspotmail.com Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation") Fixes: eddb98ad9364 ("ata: libata-eh: correctly handle deferred qc timeouts") Reviewed-by: Igor Pylypiv Reviewed-by: Damien Le Moal Signed-off-by: Niklas Cassel Signed-off-by: Greg Kroah-Hartman

ata: libata-scsi: avoid Non-NCQ command starvation

2026-03-13T16:20:23+00:00

[ Upstream commit 0ea84089dbf62a92dc7889c79e6b18fc89260808 ] 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 function ata_scsi_schedule_deferred_qc() which is called from ata_scsi_qc_complete(). This thus excludes this mechanism from all internal non-NCQ commands issued by ATA EH. When a port deferred_qc is non NULL, that is, the port has a command waiting for the device queue to drain, the issuing of all incoming commands (both NCQ and non-NCQ) is deferred using the regular busy mechanism. This simplifies the code and also avoids potential denial of service problems if a user issues too many non-NCQ commands. Finally, whenever ata EH is scheduled, regardless of the reason, a deferred qc is always requeued so that it can be retried once EH completes. This is done by calling the function ata_scsi_requeue_deferred_qc() from ata_eh_set_pending(). This avoids the need for any special processing for the deferred qc in case of NCQ error, link or device reset, or device timeout. Reported-by: Xingui Yang Reported-by: Igor Pylypiv Fixes: bdb01301f3ea ("scsi: Add host and host template flag 'host_tagset'") Cc: stable@vger.kernel.org Signed-off-by: Damien Le Moal Reviewed-by: Niklas Cassel Reviewed-by: Martin K. Petersen Reviewed-by: John Garry Tested-by: Igor Pylypiv Tested-by: Xingui Yang Signed-off-by: Sasha Levin