2019-05-03 18:15:01

by Serge Semin

Subject: [PATCH v2 4/5] mips: Make sure dt memory regions are valid

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 <[email protected]>
---
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 437a174e3ef9..28bf01961bb2 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,
--
2.21.0

2019-05-06 19:13:16

by Paul Burton

Subject: Re: [PATCH v2 4/5] mips: Make sure dt memory regions are valid

Hello,

Serge Semin wrote:
> 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 <[email protected]>

Applied to mips-next.

Thanks,
Paul

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