2014-11-06 05:42:02

by Minfei Huang

Subject: [PATCH] x86/mm: Give the correct initail value to the pmd_idx

The variable value is undefined from the stack eara. So it makes sense to
init the variable to run process correctly.

If the variable pmd_idx inits the value more than PTRS_PER_PMD, the
count may be smaller than the correct value, and the allocated page may
be not enough for pte entry.

The kernel may panic cause by the undefine variable which is allocated
from stack.

Signed-off-by: Minfei Huang <[email protected]>
---
arch/x86/mm/init_32.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index c8140e1..c23ab1e 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -137,6 +137,7 @@ page_table_range_init_count(unsigned long start, unsigned long end)

vaddr = start;
pgd_idx = pgd_index(vaddr);
+ pmd_idx = pmd_index(vaddr);

for ( ; (pgd_idx < PTRS_PER_PGD) && (vaddr != end); pgd_idx++) {
for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end);
--
1.8.3.1

2014-11-11 11:36:23

by Minfei Huang

Subject: Re: [PATCH] x86/mm: Give the correct initail value to the pmd_idx

Could someone who help me review my patch?

Thanks
Minfei

On 11/06/14 at 01:41pm, Minfei Huang wrote:
> The variable value is undefined from the stack eara. So it makes sense to
> init the variable to run process correctly.
>
> If the variable pmd_idx inits the value more than PTRS_PER_PMD, the
> count may be smaller than the correct value, and the allocated page may
> be not enough for pte entry.
>
> The kernel may panic cause by the undefine variable which is allocated
> from stack.
>
> Signed-off-by: Minfei Huang <[email protected]>
> ---
> arch/x86/mm/init_32.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
> index c8140e1..c23ab1e 100644
> --- a/arch/x86/mm/init_32.c
> +++ b/arch/x86/mm/init_32.c
> @@ -137,6 +137,7 @@ page_table_range_init_count(unsigned long start, unsigned long end)
>
> vaddr = start;
> pgd_idx = pgd_index(vaddr);
> + pmd_idx = pmd_index(vaddr);
>
> for ( ; (pgd_idx < PTRS_PER_PGD) && (vaddr != end); pgd_idx++) {
> for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end);
> --
> 1.8.3.1
>
> --
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