[PATCH] dma-debug: Fix overflow issue in bucket_find_contain

[yf.wang at mediatek.com]

From: Yunfei Wang <yf.wang at mediatek.com>

There are two issue:
1. If max_rang is set to 0xFFFF_FFFF, and __hash_bucket_find always
returns NULL, the rang will be accumulated. When rang is accumulated
to 0xFFFF_E000, after executing rang += (1 << HASH_FN_SHIFT) again,
rang will overflow to 0, making it impossible to exit the while loop.
2. dev_addr reduce maybe overflow.

So, add range and dev_addr check to avoid overflow.

Signed-off-by: jianjiao zeng <jianjiao.zeng at mediatek.com>
Signed-off-by: Yunfei Wang <yf.wang at mediatek.com>
---
 kernel/dma/debug.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index ad731f7858c9..9d7d54cd4c63 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -352,6 +352,7 @@ static struct dma_debug_entry *bucket_find_contain(struct hash_bucket **bucket,
 
 	unsigned int max_range = dma_get_max_seg_size(ref->dev);
 	struct dma_debug_entry *entry, index = *ref;
+	unsigned int shift = (1 << HASH_FN_SHIFT);
 	unsigned int range = 0;
 
 	while (range <= max_range) {
@@ -360,12 +361,15 @@ static struct dma_debug_entry *bucket_find_contain(struct hash_bucket **bucket,
 		if (entry)
 			return entry;
 
+		if (max_range - range < shift || index.dev_addr < shift)
+			return NULL;
+
 		/*
 		 * Nothing found, go back a hash bucket
 		 */
 		put_hash_bucket(*bucket, *flags);
-		range          += (1 << HASH_FN_SHIFT);
-		index.dev_addr -= (1 << HASH_FN_SHIFT);
+		range          += shift;
+		index.dev_addr -= shift;
 		*bucket = get_hash_bucket(&index, flags);
 	}
 
-- 
2.18.0