From 554af0c396380baf416f54c439b99b495180b2f4 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Wed, 7 Sep 2016 13:37:01 +0100 Subject: [PATCH] MIPS: vDSO: Fix Malta EVA mapping to vDSO page structs The page structures associated with the vDSO pages in the kernel image are calculated using virt_to_page(), which uses __pa() under the hood to find the pfn associated with the virtual address. The vDSO data pointers however point to kernel symbols, so __pa_symbol() should really be used instead. Since there is no equivalent to virt_to_page() which uses __pa_symbol(), fix init_vdso_image() to work directly with pfns, calculated with __phys_to_pfn(__pa_symbol(...)). This issue broke the Malta Enhanced Virtual Addressing (EVA) configuration which has a non-default implementation of __pa_symbol(). This is because it uses a physical alias so that the kernel executes from KSeg0 (VA 0x80000000 -> PA 0x00000000), while RAM is provided to the kernel in the KUSeg range (VA 0x00000000 -> PA 0x80000000) which uses the same underlying RAM. Since there are no page structures associated with the low physical address region, some arbitrary kernel memory would be interpreted as a page structure for the vDSO pages and badness ensues. Fixes: ebb5e78cc634 ("MIPS: Initial implementation of a VDSO") Signed-off-by: James Hogan Cc: Leonid Yegoshin Cc: linux-mips@linux-mips.org Cc: # 4.4.x- Patchwork: https://patchwork.linux-mips.org/patch/14229/ Signed-off-by: Ralf Baechle --- arch/mips/kernel/vdso.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c index 9abe447a4b480a..f9dbfb14af3358 100644 --- a/arch/mips/kernel/vdso.c +++ b/arch/mips/kernel/vdso.c @@ -39,16 +39,16 @@ static struct vm_special_mapping vdso_vvar_mapping = { static void __init init_vdso_image(struct mips_vdso_image *image) { unsigned long num_pages, i; + unsigned long data_pfn; BUG_ON(!PAGE_ALIGNED(image->data)); BUG_ON(!PAGE_ALIGNED(image->size)); num_pages = image->size / PAGE_SIZE; - for (i = 0; i < num_pages; i++) { - image->mapping.pages[i] = - virt_to_page(image->data + (i * PAGE_SIZE)); - } + data_pfn = __phys_to_pfn(__pa_symbol(image->data)); + for (i = 0; i < num_pages; i++) + image->mapping.pages[i] = pfn_to_page(data_pfn + i); } static int __init init_vdso(void)