Patch "drivers/base/memory.c: prohibit offlining of memory blocks with missing sections" has been added to the 4.3-stable tree

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

drivers/base/memory.c: prohibit offlining of memory blocks with missing sections

to the 4.3-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:
drivers-base-memory.c-prohibit-offlining-of-memory-blocks-with-missing-sections.patch
and it can be found in the queue-4.3 subdirectory.

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

From: Seth Jennings <[email protected]>
Date: Fri, 11 Dec 2015 13:40:57 -0800
Subject: drivers/base/memory.c: prohibit offlining of memory blocks with missing sections

From: Seth Jennings <[email protected]>

commit 26bbe7ef6d5cdc7ec08cba6d433fca4060f258f3 upstream.

Commit bdee237c0343 ("x86: mm: Use 2GB memory block size on large-memory x86-64 systems") and 982792c782ef ("x86, mm: probe memory block size for generic x86 64bit") introduced large block sizes for x86. This made it possible to have multiple sections per memory block where previously, there was a only every one section per block.

Since blocks consist of contiguous ranges of section, there can be holes in the blocks where sections are not present. If one attempts to offline such a block, a crash occurs since the code is not designed to deal with this.

This patch is a quick fix to gaurd against the crash by not allowing blocks with non-present sections to be offlined.

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=107781

---
 drivers/base/memory.c |    4 ++++
 1 file changed, 4 insertions(+)

@@ -303,6 +303,10 @@ static int memory_subsys_offline(struct
 	if (mem->state == MEM_OFFLINE)
 		return 0;
 
+	/* Can't offline block with non-present sections */
+	if (mem->section_count != sections_per_block)
+		return -EINVAL;
+
 	return memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
 }
 

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

queue-4.3/drivers-base-memory.c-prohibit-offlining-of-memory-blocks-with-missing-sections.patch