linux-kernel - [PATCH] ARM, xtensa: highmem: avoid clobbering non-page aligned memory reservations

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Message-Id: <20201031094345.6984-1-rppt@kernel.org>
Date:   Sat, 31 Oct 2020 11:43:45 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org, linux-xtensa@...ux-xtensa.org
Cc:     Ard Biesheuvel <ardb@...nel.org>, Chris Zankel <chris@...kel.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Max Filippov <jcmvbkbc@...il.com>,
        Mike Rapoport <rppt@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Russell King <linux@...linux.org.uk>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] ARM, xtensa: highmem: avoid clobbering non-page aligned memory reservations

From: Ard Biesheuvel <ardb@...nel.org>

free_highpages() iterates over the free memblock regions in high
memory, and marks each page as available for the memory management
system.

Until commit cddb5ddf2b76 ("arm, xtensa: simplify initialization of
high memory pages") it rounded beginning of each region upwards and end of
each region downwards.

However, after that commit free_highmem() rounds the beginning and end of
each region downwards, and we may end up freeing a page that is
memblock_reserve()d, resulting in memory corruption.

Restore the original rounding of the region boundaries to avoid freeing
reserved pages.

Fixes: cddb5ddf2b76 ("arm, xtensa: simplify initialization of high memory pages")
Link: https://lore.kernel.org/r/20201029110334.4118-1-ardb@kernel.org/
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Co-developed-by:  Mike Rapoport <rppt@...ux.ibm.com>
Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
---

Max, Russell,

Please let me know how do you prefer to take it upstream.
If needed this can go via memblock tree.

v2: fix words order in the commit message

 arch/arm/mm/init.c    | 4 ++--
 arch/xtensa/mm/init.c | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index d57112a276f5..c23dbf8bebee 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -354,8 +354,8 @@ static void __init free_highpages(void)
 	/* set highmem page free */
 	for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE,
 				&range_start, &range_end, NULL) {
-		unsigned long start = PHYS_PFN(range_start);
-		unsigned long end = PHYS_PFN(range_end);
+		unsigned long start = PFN_UP(range_start);
+		unsigned long end = PFN_DOWN(range_end);
 
 		/* Ignore complete lowmem entries */
 		if (end <= max_low)
diff --git a/arch/xtensa/mm/init.c b/arch/xtensa/mm/init.c
index c6fc83efee0c..8731b7ad9308 100644
--- a/arch/xtensa/mm/init.c
+++ b/arch/xtensa/mm/init.c
@@ -89,8 +89,8 @@ static void __init free_highpages(void)
 	/* set highmem page free */
 	for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE,
 				&range_start, &range_end, NULL) {
-		unsigned long start = PHYS_PFN(range_start);
-		unsigned long end = PHYS_PFN(range_end);
+		unsigned long start = PFN_UP(range_start);
+		unsigned long end = PFN_DOWN(range_end);
 
 		/* Ignore complete lowmem entries */
 		if (end <= max_low)
-- 
2.28.0