[PATCH 008/216] x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE

[PATCH 008/216] x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE

[Alex Shi]

From: Dexuan Cui <decui@microsoft.com>

commit d1cd1210834649ce1ca6bafe5ac25d2f40331343 upstream.

pte_pfn() returns a PFN of long (32 bits in 32-PAE), so "long <<
PAGE_SHIFT" will overflow for PFNs above 4GB.

Due to this issue, some Linux 32-PAE distros, running as guests on Hyper-V,
with 5GB memory assigned, can't load the netvsc driver successfully and
hence the synthetic network device can't work (we can use the kernel parameter
mem=3000M to work around the issue).

Cast pte_pfn() to phys_addr_t before shifting.

Fixes: "commit d76565344512: x86, mm: Create slow_virt_to_phys()"
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: gregkh@linuxfoundation.org
Cc: linux-mm@kvack.org
Cc: olaf@aepfle.de
Cc: apw@canonical.com
Cc: jasowang@redhat.com
Cc: dave.hansen@intel.com
Cc: riel@redhat.com
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1414580017-27444-1-git-send-email-decui@microsoft.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
---
 7u/arch/x86/mm/pageattr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/7u/arch/x86/mm/pageattr.c b/7u/arch/x86/mm/pageattr.c
index 4ed2b2d..81b82f4 100644
--- a/7u/arch/x86/mm/pageattr.c
+++ b/7u/arch/x86/mm/pageattr.c
@@ -405,7 +405,7 @@ phys_addr_t slow_virt_to_phys(void *__virt_addr)
 	psize = page_level_size(level);
 	pmask = page_level_mask(level);
 	offset = virt_addr & ~pmask;
-	phys_addr = pte_pfn(*pte) << PAGE_SHIFT;
+	phys_addr = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
 	return (phys_addr | offset);
 }
 EXPORT_SYMBOL_GPL(slow_virt_to_phys);
-- 
1.8.3.1

Re: [PATCH 008/216] x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE

[Alex Shi]

Hi, All,

Please ignore this stupid email thread. I thought I had suppressed cc in gitconfig. But I am wrong...

Very very sorry!


Thanks
Alex

On 2018/11/28 7:29 PM, Alex Shi wrote:
> From: Dexuan Cui <decui@microsoft.com>
>
> commit d1cd1210834649ce1ca6bafe5ac25d2f40331343 upstream.
>
> pte_pfn() returns a PFN of long (32 bits in 32-PAE), so "long <<
> PAGE_SHIFT" will overflow for PFNs above 4GB.
>
> Due to this issue, some Linux 32-PAE distros, running as guests on Hyper-V,
> with 5GB memory assigned, can't load the netvsc driver successfully and
> hence the synthetic network device can't work (we can use the kernel parameter
> mem=3000M to work around the issue).
>
> Cast pte_pfn() to phys_addr_t before shifting.
>
> Fixes: "commit d76565344512: x86, mm: Create slow_virt_to_phys()"
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: gregkh@linuxfoundation.org
> Cc: linux-mm@kvack.org
> Cc: olaf@aepfle.de
> Cc: apw@canonical.com
> Cc: jasowang@redhat.com
> Cc: dave.hansen@intel.com
> Cc: riel@redhat.com
> Cc: stable@vger.kernel.org
> Link: http://lkml.kernel.org/r/1414580017-27444-1-git-send-email-decui@microsoft.com
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
> ---
>  7u/arch/x86/mm/pageattr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/7u/arch/x86/mm/pageattr.c b/7u/arch/x86/mm/pageattr.c
> index 4ed2b2d..81b82f4 100644
> --- a/7u/arch/x86/mm/pageattr.c
> +++ b/7u/arch/x86/mm/pageattr.c
> @@ -405,7 +405,7 @@ phys_addr_t slow_virt_to_phys(void *__virt_addr)
>  	psize = page_level_size(level);
>  	pmask = page_level_mask(level);
>  	offset = virt_addr & ~pmask;
> -	phys_addr = pte_pfn(*pte) << PAGE_SHIFT;
> +	phys_addr = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
>  	return (phys_addr | offset);
>  }
>  EXPORT_SYMBOL_GPL(slow_virt_to_phys);