Patch "MIPS: vDSO: Fix Malta EVA mapping to vDSO page structs" has been added to the 4.4-stable tree

Patch "MIPS: vDSO: Fix Malta EVA mapping to vDSO page structs" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    MIPS: vDSO: Fix Malta EVA mapping to vDSO page structs

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mips-vdso-fix-malta-eva-mapping-to-vdso-page-structs.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 554af0c396380baf416f54c439b99b495180b2f4 Mon Sep 17 00:00:00 2001
From: James Hogan <james.hogan@imgtec.com>
Date: Wed, 7 Sep 2016 13:37:01 +0100
Subject: MIPS: vDSO: Fix Malta EVA mapping to vDSO page structs

From: James Hogan <james.hogan@imgtec.com>

commit 554af0c396380baf416f54c439b99b495180b2f4 upstream.

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 <james.hogan@imgtec.com>
Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14229/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/vdso.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/mips/kernel/vdso.c
+++ b/arch/mips/kernel/vdso.c
@@ -39,16 +39,16 @@ static struct vm_special_mapping vdso_vv
 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)


Patches currently in stable-queue which might be from james.hogan@imgtec.com are

queue-4.4/mips-vdso-fix-malta-eva-mapping-to-vdso-page-structs.patch