linux-kernel - [PATCH AUTOSEL 4.19 053/141] mips: Make sure dt memory regions are valid

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Date:   Sat,  1 Jun 2019 09:20:29 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Serge Semin <fancer.lancer@...il.com>,
        Paul Burton <paul.burton@...s.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Bogendoerfer <tbogendoerfer@...e.de>,
        Huacai Chen <chenhc@...ote.com>,
        Stefan Agner <stefan@...er.ch>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Juergen Gross <jgross@...e.com>,
        Serge Semin <Sergey.Semin@...latforms.ru>,
        linux-mips@...r.kernel.org, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.19 053/141] mips: Make sure dt memory regions are valid

From: Serge Semin <fancer.lancer@...il.com>

[ Upstream commit 93fa5b280761a4dbb14c5330f260380385ab2b49 ]

There are situations when memory regions coming from dts may be
too big for the platform physical address space. This especially
concerns XPA-capable systems. Bootloader may determine more than 4GB
memory available and pass it to the kernel over dts memory node, while
kernel is built without XPA/64BIT support. In this case the region
may either simply be truncated by add_memory_region() method
or by u64->phys_addr_t type casting. But in worst case the method
can even drop the memory region if it exceeds PHYS_ADDR_MAX size.
So lets make sure the retrieved from dts memory regions are valid,
and if some of them aren't, just manually truncate them with a warning
printed out.

Signed-off-by: Serge Semin <fancer.lancer@...il.com>
Signed-off-by: Paul Burton <paul.burton@...s.com>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: James Hogan <jhogan@...nel.org>
Cc: Mike Rapoport <rppt@...ux.ibm.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Thomas Bogendoerfer <tbogendoerfer@...e.de>
Cc: Huacai Chen <chenhc@...ote.com>
Cc: Stefan Agner <stefan@...er.ch>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Serge Semin <Sergey.Semin@...latforms.ru>
Cc: linux-mips@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/mips/kernel/prom.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kernel/prom.c b/arch/mips/kernel/prom.c
index 89950b7bf536b..bdaf3536241a2 100644
--- a/arch/mips/kernel/prom.c
+++ b/arch/mips/kernel/prom.c
@@ -41,7 +41,19 @@ char *mips_get_machine_name(void)
 #ifdef CONFIG_USE_OF
 void __init early_init_dt_add_memory_arch(u64 base, u64 size)
 {
-	return add_memory_region(base, size, BOOT_MEM_RAM);
+	if (base >= PHYS_ADDR_MAX) {
+		pr_warn("Trying to add an invalid memory region, skipped\n");
+		return;
+	}
+
+	/* Truncate the passed memory region instead of type casting */
+	if (base + size - 1 >= PHYS_ADDR_MAX || base + size < base) {
+		pr_warn("Truncate memory region %llx @ %llx to size %llx\n",
+			size, base, PHYS_ADDR_MAX - base);
+		size = PHYS_ADDR_MAX - base;
+	}
+
+	add_memory_region(base, size, BOOT_MEM_RAM);
 }
 
 int __init early_init_dt_reserve_memory_arch(phys_addr_t base,
-- 
2.20.1