[PATCH 3/3] drivers: memory: prohibit offlining of memory blocks with missing sections

From: Seth Jennings <sjennings@variantweb.net>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Seth Jennings <sjennings@variantweb.net>,
	Andrew Banman <abanman@sgi.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Russ Anderson <rja@sgi.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH 3/3] drivers: memory: prohibit offlining of memory blocks with missing sections
Date: Wed,  2 Dec 2015 09:07:01 -0600	[thread overview]
Message-ID: <1449068821-9870-3-git-send-email-sjennings@variantweb.net> (raw)
In-Reply-To: <1449068821-9870-1-git-send-email-sjennings@variantweb.net>

bdee237c and 982792c7 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.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=107781
Reported-by: Andrew Banman <abanman@sgi.com>
Signed-off-by: Seth Jennings <sjennings@variantweb.net>
---
 drivers/base/memory.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index dd30744..6d7b14c 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -303,6 +303,10 @@ static int memory_subsys_offline(struct device *dev)
 	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);
 }
 
-- 
2.5.0
