linux-kernel - [PATCH] powerpc/msi: Remove VLA usage

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Date:   Fri, 29 Jun 2018 11:52:54 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>,
        Rob Herring <robh@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH] powerpc/msi: Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this
switches from an unchanging variable to a constant expression to eliminate
the VLA generation.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>
Cc: Rob Herring <robh@...nel.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: linuxppc-dev@...ts.ozlabs.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/powerpc/sysdev/msi_bitmap.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/sysdev/msi_bitmap.c b/arch/powerpc/sysdev/msi_bitmap.c
index 6243a7e537d0..e64a411d1a00 100644
--- a/arch/powerpc/sysdev/msi_bitmap.c
+++ b/arch/powerpc/sysdev/msi_bitmap.c
@@ -225,22 +225,23 @@ static void __init test_of_node(void)
 	struct device_node of_node;
 	struct property prop;
 	struct msi_bitmap bmp;
-	int size = 256;
-	DECLARE_BITMAP(expected, size);
+#define SIZE_EXPECTED 256
+	DECLARE_BITMAP(expected, SIZE_EXPECTED);
 
 	/* There should really be a struct device_node allocator */
 	memset(&of_node, 0, sizeof(of_node));
 	of_node_init(&of_node);
 	of_node.full_name = node_name;
 
-	WARN_ON(msi_bitmap_alloc(&bmp, size, &of_node));
+	WARN_ON(msi_bitmap_alloc(&bmp, SIZE_EXPECTED, &of_node));
 
 	/* No msi-available-ranges, so expect > 0 */
 	WARN_ON(msi_bitmap_reserve_dt_hwirqs(&bmp) <= 0);
 
 	/* Should all still be free */
-	WARN_ON(bitmap_find_free_region(bmp.bitmap, size, get_count_order(size)));
-	bitmap_release_region(bmp.bitmap, 0, get_count_order(size));
+	WARN_ON(bitmap_find_free_region(bmp.bitmap, SIZE_EXPECTED,
+					get_count_order(SIZE_EXPECTED)));
+	bitmap_release_region(bmp.bitmap, 0, get_count_order(SIZE_EXPECTED));
 
 	/* Now create a fake msi-available-ranges property */
 
@@ -256,8 +257,8 @@ static void __init test_of_node(void)
 	WARN_ON(msi_bitmap_reserve_dt_hwirqs(&bmp));
 
 	/* Check we got the expected result */
-	WARN_ON(bitmap_parselist(expected_str, expected, size));
-	WARN_ON(!bitmap_equal(expected, bmp.bitmap, size));
+	WARN_ON(bitmap_parselist(expected_str, expected, SIZE_EXPECTED));
+	WARN_ON(!bitmap_equal(expected, bmp.bitmap, SIZE_EXPECTED));
 
 	msi_bitmap_free(&bmp);
 	kfree(bmp.bitmap);
-- 
2.17.1


-- 
Kees Cook
Pixel Security