| From d1cd1210834649ce1ca6bafe5ac25d2f40331343 Mon Sep 17 00:00:00 2001 |
| From: Dexuan Cui <decui@microsoft.com> |
| Date: Wed, 29 Oct 2014 03:53:37 -0700 |
| Subject: x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE |
| |
| 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> |
| |
| --- |
| arch/x86/mm/pageattr.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/arch/x86/mm/pageattr.c |
| +++ b/arch/x86/mm/pageattr.c |
| @@ -409,7 +409,7 @@ phys_addr_t slow_virt_to_phys(void *__vi |
| 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); |