Patch "mm/cma: make kmemleak ignore CMA regions" has been added to the 3.18-stable tree

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

mm/cma: make kmemleak ignore CMA regions

to the 3.18-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:
mm-cma-make-kmemleak-ignore-cma-regions.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Thierry Reding <[email protected]>
Date: Fri, 12 Dec 2014 16:58:31 -0800
Subject: mm/cma: make kmemleak ignore CMA regions

From: Thierry Reding <[email protected]>

commit 620951e2745750de1482128615adc15b74ee37ed upstream.

kmemleak will add allocations as objects to a pool. The memory allocated for each object in this pool is periodically searched for pointers to other allocated objects. This only works for memory that is mapped into the kernel's virtual address space, which happens not to be the case for most CMA regions.

Furthermore, CMA regions are typically used to store data transferred to or from a device and therefore don't contain pointers to other objects.

Without this, the kernel crashes on the first execution of the scan_gray_list() because it tries to access highmem. Perhaps a more appropriate fix would be to reject any object that can't map to a kernel virtual address?

---
 mm/cma.c |    6 ++++++
 1 file changed, 6 insertions(+)

@@ -33,6 +33,7 @@
 #include <linux/log2.h>
 #include <linux/cma.h>
 #include <linux/highmem.h>
+#include <linux/io.h>
 
 struct cma {
 	unsigned long	base_pfn;

@@ -325,6 +326,11 @@ int __init cma_declare_contiguous(phys_a
 			}
 		}
 
+		/*
+		 * kmemleak scans/reads tracked objects for pointers to other
+		 * objects but this address isn't mapped and accessible
+		 */
+		kmemleak_ignore(phys_to_virt(addr));
 		base = addr;
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/mm-cma-make-kmemleak-ignore-cma-regions.patch