[PATCH] drivers/base/memory.c: Fix "mm/memory_hotplug: Move and simplify walk_memory_blocks()"

David Hildenbrand
2019-06-21T19:38:42Z

The start and the size are 0 for online nodes without any memory. Avoid
the underflow, resulting in a very long loop and soft lockups.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: linux-mm@kvack.org
Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: David Hildenbrand <david@redhat.com>
---

@Andrew, Stephen - sorry for the noise *again*. Feel feel to either apply
this patch or drop the respective patches for now.

---
drivers/base/memory.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 972c5336bebf..7595a4f0068f 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -868,6 +868,9 @@ int walk_memory_blocks(unsigned long start, unsigned long size,
unsigned long block_id;
int ret = 0;

+ if (!size)
+ return 0;
+
for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
mem = find_memory_block_by_id(block_id);
if (!mem)
--
2.21.0