[PATCH 3.16.y-ckt 045/128] drivers/base/memory.c: prohibit offlining of memory blocks with missing sections

From: Luis Henriques
Date: Sun Jan 24 2016 - 17:30:57 EST

3.16.7-ckt23 -stable review patch. If anyone has any objections, please let me know.


From: Seth Jennings <sjennings@xxxxxxxxxxxxxx>

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

Signed-off-by: Seth Jennings <sjennings@xxxxxxxxxxxxxx>
Reported-by: Andrew Banman <abanman@xxxxxxx>
Cc: Daniel J Blueman <daniel@xxxxxxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Greg KH <greg@xxxxxxxxx>
Cc: Russ Anderson <rja@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
drivers/base/memory.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 89f752dd8465..0b5c02ab1ef0 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -301,6 +301,10 @@ 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);