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From:   Marek Szyprowski <m.szyprowski@samsung.com>
To:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Cc:     Marek Szyprowski <m.szyprowski@samsung.com>,
        Russell King <linux@armlinux.org.uk>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@kernel.org>
Subject: [PATCH] arm: dma-mapping: don't call folio_next() beyond the
 requested region
Date:   Thu, 10 Aug 2023 11:19:55 +0200
Message-Id: <20230810091955.3579004-1-m.szyprowski@samsung.com>
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References: <CGME20230810092017eucas1p23930e5e5ec443ac7776002f2f09967d4@eucas1p2.samsung.com>
Precedence: bulk

Add a check for the non-zero offset case to avoid calling folio_next()
beyond the requested region and relying on its parameters.

Fixes: cc24e9c0895c ("arm: implement the new page table range API")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
---
 arch/arm/mm/dma-mapping.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 0474840224d9..6c952d6899f2 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -715,6 +715,8 @@ static void __dma_page_dev_to_cpu(struct page *page, unsigned long off,
 
 		if (offset) {
 			left -= folio_size(folio) - offset;
+			if (left <= 0)
+				return;
 			folio = folio_next(folio);
 		}
 
-- 
2.34.1