x86, pageattr: fix slow_virt_to_phys() for X86_PAE
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PATCH 1/1 x86, pageattr: fix slow_virt_to_phys() for X86_PAE
pte_pfn() returns a PFN of long (32 bits in 32-PAE), then "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).
--- arch/x86/mm/pageattr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
arch/x86/mm/pageattr.c +1 -1
@@ -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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tip-bot for Dexuan Cui
merge bot[tip:x86/urgent] x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE
x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE
Commit-ID: d1cd1210834649ce1ca6bafe5ac25d2f40331343 Gitweb: http://git.kernel.org/tip/d1cd1210834649ce1ca6bafe5ac25d2f40331343 Author: Dexuan Cui <[email protected]> AuthorDate: Wed, 29 Oct 2014 03:53:37 -0700 Committer: Thomas Gleixner <[email protected]> CommitDate: Wed, 29 Oct 2014 10:57:21 +0100
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.
--- arch/x86/mm/pageattr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
arch/x86/mm/pageattr.c +1 -1
@@ -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);