Commit d1cd1210 authored Oct 29, 2014 by Dexuan Cui Committed by Thomas Gleixner Oct 29, 2014

x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE



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 d7656534: 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>

parent b77e8f43

arch/x86/mm/pageattr.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -409,7 +409,7 @@ 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);

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