linux-kernel - [PATCH 2/2] mm/memblock.c: check return value of memblock_reserve() in memblock_virt_alloc

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Date:   Wed, 21 Dec 2016 23:30:33 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     trivial@...nel.org, akpm@...ux-foundation.org, mhocko@...nel.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Wei Yang <richard.weiyang@...il.com>
Subject: [PATCH 2/2] mm/memblock.c: check return value of memblock_reserve() in memblock_virt_alloc_internal()

memblock_reserve() would add a new range to memblock.reserved in case the
new range is not totally covered by any of the current memblock.reserved
range. If the memblock.reserved is full and can't resize,
memblock_reserve() would fail.

This doesn't happen in real world now, I observed this during code review.
While theoretically, it has the chance to happen. And if it happens, others
would think this range of memory is still available and may corrupt the
memory.

This patch checks the return value and goto "done" after it succeeds.

Signed-off-by: Wei Yang <richard.weiyang@...il.com>
---
 mm/memblock.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index 4929e06..d0f2c96 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1274,18 +1274,17 @@ static void * __init memblock_virt_alloc_internal(
 
 	if (max_addr > memblock.current_limit)
 		max_addr = memblock.current_limit;
-
 again:
 	alloc = memblock_find_in_range_node(size, align, min_addr, max_addr,
 					    nid, flags);
-	if (alloc)
+	if (alloc && !memblock_reserve(alloc, size))
 		goto done;
 
 	if (nid != NUMA_NO_NODE) {
 		alloc = memblock_find_in_range_node(size, align, min_addr,
 						    max_addr, NUMA_NO_NODE,
 						    flags);
-		if (alloc)
+		if (alloc && !memblock_reserve(alloc, size))
 			goto done;
 	}
 
@@ -1303,7 +1302,6 @@ static void * __init memblock_virt_alloc_internal(
 
 	return NULL;
 done:
-	memblock_reserve(alloc, size);
 	ptr = phys_to_virt(alloc);
 	memset(ptr, 0, size);
 
-- 
2.5.0