linux-kernel - [PATCH AUTOSEL 4.19 04/11] of: Fix reserved-memory overlap detection

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Date:   Mon,  2 Nov 2020 20:20:32 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Vincent Whitchurch <vincent.whitchurch@...s.com>,
        Rob Herring <robh@...nel.org>, Sasha Levin <sashal@...nel.org>,
        devicetree@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 04/11] of: Fix reserved-memory overlap detection

From: Vincent Whitchurch <vincent.whitchurch@...s.com>

[ Upstream commit ca05f33316559a04867295dd49f85aeedbfd6bfd ]

The reserved-memory overlap detection code fails to detect overlaps if
either of the regions starts at address 0x0.  The code explicitly checks
for and ignores such regions, apparently in order to ignore dynamically
allocated regions which have an address of 0x0 at this point.  These
dynamically allocated regions also have a size of 0x0 at this point, so
fix this by removing the check and sorting the dynamically allocated
regions ahead of any static regions at address 0x0.

For example, there are two overlaps in this case but they are not
currently reported:

	foo@0 {
	        reg = <0x0 0x2000>;
	};

	bar@0 {
	        reg = <0x0 0x1000>;
	};

	baz@...0 {
	        reg = <0x1000 0x1000>;
	};

	quux {
	        size = <0x1000>;
	};

but they are after this patch:

 OF: reserved mem: OVERLAP DETECTED!
 bar@0 (0x00000000--0x00001000) overlaps with foo@0 (0x00000000--0x00002000)
 OF: reserved mem: OVERLAP DETECTED!
 foo@0 (0x00000000--0x00002000) overlaps with baz@...0 (0x00001000--0x00002000)

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
Link: https://lore.kernel.org/r/ded6fd6b47b58741aabdcc6967f73eca6a3f311e.1603273666.git-series.vincent.whitchurch@axis.com
Signed-off-by: Rob Herring <robh@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/of/of_reserved_mem.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 895c83e0c7b6c..19f95552da4d8 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -218,6 +218,16 @@ static int __init __rmem_cmp(const void *a, const void *b)
 	if (ra->base > rb->base)
 		return 1;
 
+	/*
+	 * Put the dynamic allocations (address == 0, size == 0) before static
+	 * allocations at address 0x0 so that overlap detection works
+	 * correctly.
+	 */
+	if (ra->size < rb->size)
+		return -1;
+	if (ra->size > rb->size)
+		return 1;
+
 	return 0;
 }
 
@@ -235,8 +245,7 @@ static void __init __rmem_check_for_overlap(void)
 
 		this = &reserved_mem[i];
 		next = &reserved_mem[i + 1];
-		if (!(this->base && next->base))
-			continue;
+
 		if (this->base + this->size > next->base) {
 			phys_addr_t this_end, next_end;
 
-- 
2.27.0