VisionFive2 Linux kernel

StarFive Tech Linux Kernel for VisionFive (JH7110) boards (mirror)

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author: Tvrtko Ursulin <tvrtko.ursulin@intel.com> 2017-08-03 10:13:12 +0100 committer: Tvrtko Ursulin <tvrtko.ursulin@intel.com> 2017-09-07 10:48:28 +0100 commit: c125906b839b794c580a5de911de65bd2c63aaee parent: c4860ad60564838994b74e7ee7dd12ceeda0f520
Commit Summary:
lib/scatterlist: Avoid potential scatterlist entry overflow
Diffstat:
1 file changed, 20 insertions, 11 deletions
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index dee0c5004e2f..7b2e74da2c44 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -394,17 +394,22 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
 	unsigned int offset, unsigned long size,
 	gfp_t gfp_mask)
 {
-	unsigned int chunks;
-	unsigned int i;
-	unsigned int cur_page;
+	const unsigned int max_segment = SCATTERLIST_MAX_SEGMENT;
+	unsigned int chunks, cur_page, seg_len, i;
 	int ret;
 	struct scatterlist *s;
 
 	/* compute number of contiguous chunks */
 	chunks = 1;
-	for (i = 1; i < n_pages; ++i)
-		if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1)
-			++chunks;
+	seg_len = 0;
+	for (i = 1; i < n_pages; i++) {
+		seg_len += PAGE_SIZE;
+		if (seg_len >= max_segment ||
+		    page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) {
+			chunks++;
+			seg_len = 0;
+		}
+	}
 
 	ret = sg_alloc_table(sgt, chunks, gfp_mask);
 	if (unlikely(ret))
@@ -413,17 +418,21 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
 	/* merging chunks and putting them into the scatterlist */
 	cur_page = 0;
 	for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
-		unsigned long chunk_size;
-		unsigned int j;
+		unsigned int j, chunk_size;
 
 		/* look for the end of the current chunk */
-		for (j = cur_page + 1; j < n_pages; ++j)
-			if (page_to_pfn(pages[j]) !=
+		seg_len = 0;
+		for (j = cur_page + 1; j < n_pages; j++) {
+			seg_len += PAGE_SIZE;
+			if (seg_len >= max_segment ||
+			    page_to_pfn(pages[j]) !=
 			    page_to_pfn(pages[j - 1]) + 1)
 				break;
+		}
 
 		chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
-		sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);
+		sg_set_page(s, pages[cur_page],
+			    min_t(unsigned long, size, chunk_size), offset);
 		size -= chunk_size;
 		offset = 0;
 		cur_page = j;