Patch "mm/page_alloc: Remove kernel address exposure in free_reserved_area()" has been added to the 4.4-stable tree

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

mm/page_alloc: Remove kernel address exposure in free_reserved_area()

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:
mm-page_alloc-remove-kernel-address-exposure-in-free_reserved_area.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 <[email protected]> know about it.

From: Josh Poimboeuf <[email protected]>
Date: Tue, 25 Oct 2016 09:51:14 -0500
Subject: mm/page_alloc: Remove kernel address exposure in free_reserved_area()

From: Josh Poimboeuf <[email protected]>

commit adb1fe9ae2ee6ef6bc10f3d5a588020e7664dfa7 upstream.

Linus suggested we try to remove some of the low-hanging fruit related to kernel address exposure in dmesg. The only leaks I see on my local system are:

Freeing SMP alternatives memory: 32K (ffffffff9e309000 - ffffffff9e311000) Freeing initrd memory: 10588K (ffffa0b736b42000 - ffffa0b737599000) Freeing unused kernel memory: 3592K (ffffffff9df87000 - ffffffff9e309000) Freeing unused kernel memory: 1352K (ffffa0b7288ae000 - ffffa0b728a00000) Freeing unused kernel memory: 632K (ffffa0b728d62000 - ffffa0b728e00000)

Linus says:

"I suspect we should just remove [the addresses in the 'Freeing'
messages]. I'm sure they are useful in theory, but I suspect they were more useful back when the whole "free init memory" was originally done.

These days, if we have a use-after-free, I suspect the init-mem situation is the easiest situation by far. Compared to all the dynamic allocations which are much more likely to show it anyway. So having debug output for that case is likely not all that productive."

With this patch the freeing messages now look like this:

Freeing SMP alternatives memory: 32K
Freeing initrd memory: 10588K
Freeing unused kernel memory: 3592K
Freeing unused kernel memory: 1352K
Freeing unused kernel memory: 632K

---
 mm/page_alloc.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -5847,8 +5847,8 @@ unsigned long free_reserved_area(void *s
 	}
 
 	if (pages && s)
-		pr_info("Freeing %s memory: %ldK (%p - %p)\n",
-			s, pages << (PAGE_SHIFT - 10), start, end);
+		pr_info("Freeing %s memory: %ldK\n",
+			s, pages << (PAGE_SHIFT - 10));
 
 	return pages;
 }

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

queue-4.4/mm-page_alloc-remove-kernel-address-exposure-in-free_reserved_area.patch