From: Marc Zyngier <marc.zyngier@arm.com>
Date: Fri, 22 Jun 2018 10:52:52 +0100
Subject: irqchip/gic-v3-its: Only emit SYNC if targetting a valid collection
Git-commit: 83559b47cdc4d396fc1187a13b527d01b55e0fe6
Patch-mainline: v4.18-rc2
References: bsc#1111147

It is possible, under obscure circumstances, to convince the ITS driver to
emit a SYNC operation that targets a collection that is not bound to any
redistributor (and the target_address field is zero) because the
corresponding CPU has not been seen yet (the system has been booted with
max_cpus="something small").

If the ITS is using the linear CPU number as the target, this is not a big
deal, as we just end-up issuing a SYNC to CPU0. But if the ITS requires the
physical address of the redistributor (with GITS_TYPER.PTA==1), we end-up
asking the ITS to write to the physical address zero, which is not exactly
a good idea (there has been report of the ITS locking up). This should of
course never happen, but hey, this is SW...

In order to avoid the above disaster, let's track which collections have
been actually initialized, and let's not generate a SYNC if the collection
hasn't been properly bound to a redistributor.  Take this opportunity to
spit our a warning, in the hope that someone may report the issue if it
arrises again.

Reported-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Sumit Garg <sumit.garg@linaro.org>
Link: https://lkml.kernel.org/r/20180622095254.5906-6-marc.zyngier@arm.com
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
---
 drivers/irqchip/irq-gic-v3-its.c |   25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -178,6 +178,14 @@ static struct its_collection *dev_event_
 	return its->collections + its_dev->event_map.col_map[event];
 }
 
+static struct its_collection *valid_col(struct its_collection *col)
+{
+	if (WARN_ON_ONCE(col->target_address & GENMASK_ULL(0, 15)))
+		return NULL;
+
+	return col;
+}
+
 /*
  * ITS command descriptors - parameters to be encoded in a command
  * block.
@@ -435,7 +443,7 @@ static struct its_collection *its_build_
 
 	its_fixup_cmd(cmd);
 
-	return col;
+	return valid_col(col);
 }
 
 static struct its_collection *its_build_movi_cmd(struct its_node *its,
@@ -454,7 +462,7 @@ static struct its_collection *its_build_
 
 	its_fixup_cmd(cmd);
 
-	return col;
+	return valid_col(col);
 }
 
 static struct its_collection *its_build_discard_cmd(struct its_node *its,
@@ -472,7 +480,7 @@ static struct its_collection *its_build_
 
 	its_fixup_cmd(cmd);
 
-	return col;
+	return valid_col(col);
 }
 
 static struct its_collection *its_build_inv_cmd(struct its_node *its,
@@ -490,7 +498,7 @@ static struct its_collection *its_build_
 
 	its_fixup_cmd(cmd);
 
-	return col;
+	return valid_col(col);
 }
 
 static struct its_collection *its_build_int_cmd(struct its_node *its,
@@ -508,7 +516,7 @@ static struct its_collection *its_build_
 
 	its_fixup_cmd(cmd);
 
-	return col;
+	return valid_col(col);
 }
 
 static struct its_collection *its_build_clear_cmd(struct its_node *its,
@@ -526,7 +534,7 @@ static struct its_collection *its_build_
 
 	its_fixup_cmd(cmd);
 
-	return col;
+	return valid_col(col);
 }
 
 static struct its_collection *its_build_invall_cmd(struct its_node *its,
@@ -1819,11 +1827,16 @@ static int its_alloc_tables(struct its_n
 
 static int its_alloc_collections(struct its_node *its)
 {
+	int i;
+
 	its->collections = kzalloc(nr_cpu_ids * sizeof(*its->collections),
 				   GFP_KERNEL);
 	if (!its->collections)
 		return -ENOMEM;
 
+	for (i = 0; i < nr_cpu_ids; i++)
+		its->collections[i].target_address = ~0ULL;
+
 	return 0;
 }