Patch "iommu/arm-smmu: Fix CMDQ error handling" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

iommu/arm-smmu: Fix CMDQ error handling

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
iommu-arm-smmu-fix-cmdq-error-handling.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Will Deacon <[email protected]>
Date: Fri, 29 Jul 2016 11:15:37 +0100
Subject: iommu/arm-smmu: Fix CMDQ error handling

From: Will Deacon <[email protected]>

commit aea2037e0d3e23c3be1498feae29f71ca997d9e6 upstream.

In the unlikely event of a global command queue error, the ARM SMMUv3 driver attempts to convert the problematic command into a CMD_SYNC and resume the command queue. Unfortunately, this code is pretty badly broken:

1. It uses the index into the error string table as the CMDQ index, so we probably read the wrong entry out of the queue

2. The arguments to queue_write are the wrong way round, so we end up writing from the queue onto the stack.

These happily cancel out, so the kernel is likely to stay alive, but the command queue will probably fault again when we resume.

This patch fixes the error handling code to use the correct queue index and write back the CMD_SYNC to the faulting entry.

---
 drivers/iommu/arm-smmu-v3.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -870,7 +870,7 @@ static void arm_smmu_cmdq_skip_err(struc
 	 * We may have concurrent producers, so we need to be careful
 	 * not to touch any of the shadow cmdq state.
 	 */
-	queue_read(cmd, Q_ENT(q, idx), q->ent_dwords);
+	queue_read(cmd, Q_ENT(q, cons), q->ent_dwords);
 	dev_err(smmu->dev, "skipping command in error state:\n");
 	for (i = 0; i < ARRAY_SIZE(cmd); ++i)
 		dev_err(smmu->dev, "\t0x%016llx\n", (unsigned long long)cmd[i]);

@@ -881,7 +881,7 @@ static void arm_smmu_cmdq_skip_err(struc
 		return;
 	}
 
-	queue_write(cmd, Q_ENT(q, idx), q->ent_dwords);
+	queue_write(Q_ENT(q, cons), cmd, q->ent_dwords);
 }
 
 static void arm_smmu_cmdq_issue_cmd(struct arm_smmu_device *smmu,

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/arm64-define-at_vector_size_arch-for-arch_dlinfo.patch queue-4.4/iommu-arm-smmu-don-t-bug-if-we-find-aborting-stes-with-disable_bypass.patch queue-4.4/iommu-arm-smmu-fix-cmdq-error-handling.patch