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[3.8.y.z,extended,stable] Patch "powerpc/crashdump : Fix page frame number check in copy_oldmem_page" has been added to staging queue

Message ID 1395695993-28329-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa March 24, 2014, 9:19 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    powerpc/crashdump : Fix page frame number check in copy_oldmem_page

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.20.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From 7c1361d83af4f8c0d8513cde15b5b7c344cfcbce Mon Sep 17 00:00:00 2001
From: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Date: Mon, 24 Feb 2014 17:30:55 +0100
Subject: powerpc/crashdump : Fix page frame number check in copy_oldmem_page

commit f5295bd8ea8a65dc5eac608b151386314cb978f1 upstream.

In copy_oldmem_page, the current check using max_pfn and min_low_pfn to
decide if the page is backed or not, is not valid when the memory layout is
not continuous.

This happens when running as a QEMU/KVM guest, where RTAS is mapped higher
in the memory. In that case max_pfn points to the end of RTAS, and a hole
between the end of the kdump kernel and RTAS is not backed by PTEs. As a
consequence, the kdump kernel is crashing in copy_oldmem_page when accessing
in a direct way the pages in that hole.

This fix relies on the memblock's service memblock_is_region_memory to
check if the read page is part or not of the directly accessible memory.

Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Tested-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 arch/powerpc/kernel/crash_dump.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--
1.8.3.2
diff mbox

Patch

diff --git a/arch/powerpc/kernel/crash_dump.c b/arch/powerpc/kernel/crash_dump.c
index b3ba516..9d6a4a4 100644
--- a/arch/powerpc/kernel/crash_dump.c
+++ b/arch/powerpc/kernel/crash_dump.c
@@ -108,17 +108,19 @@  ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 			size_t csize, unsigned long offset, int userbuf)
 {
 	void  *vaddr;
+	phys_addr_t paddr;

 	if (!csize)
 		return 0;

 	csize = min_t(size_t, csize, PAGE_SIZE);
+	paddr = pfn << PAGE_SHIFT;

-	if ((min_low_pfn < pfn) && (pfn < max_pfn)) {
-		vaddr = __va(pfn << PAGE_SHIFT);
+	if (memblock_is_region_memory(paddr, csize)) {
+		vaddr = __va(paddr);
 		csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
 	} else {
-		vaddr = __ioremap(pfn << PAGE_SHIFT, PAGE_SIZE, 0);
+		vaddr = __ioremap(paddr, PAGE_SIZE, 0);
 		csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
 		iounmap(vaddr);
 	}