From: Robin Murphy <robin.murphy@arm.com>
Date: Thu, 1 Oct 2015 22:37:19 +0000 (-0700)
Subject: dmapool: fix overflow condition in pool_find_page()
X-Git-Tag: v4.9.8~3464^2
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=676bd99178cd962ed24ffdad222b7069d330a969;p=platform%2Fkernel%2Flinux-rpi3.git

dmapool: fix overflow condition in pool_find_page()

If a DMA pool lies at the very top of the dma_addr_t range (as may
happen with an IOMMU involved), the calculated end address of the pool
wraps around to zero, and page lookup always fails.

Tweak the relevant calculation to be overflow-proof.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Sakari Ailus <sakari.ailus@iki.fi>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/dmapool.c b/mm/dmapool.c
index 71a8998..312a716 100644
--- a/mm/dmapool.c
+++ b/mm/dmapool.c
@@ -394,7 +394,7 @@ static struct dma_page *pool_find_page(struct dma_pool *pool, dma_addr_t dma)
 	list_for_each_entry(page, &pool->page_list, page_list) {
 		if (dma < page->dma)
 			continue;
-		if (dma < (page->dma + pool->allocation))
+		if ((dma - page->dma) < pool->allocation)
 			return page;
 	}
 	return NULL;