From 286c21de32b904131f8cf6a36ce40b8b0c9c5da3 Mon Sep 17 00:00:00 2001
From: Kevin Grandemange <kevin.grandemange@allegrodvt.com>
Date: Thu, 12 Mar 2020 15:41:45 +0000
Subject: [PATCH] dma-coherent: fix integer overflow in the reserved-memory dma allocation
Git-commit: 286c21de32b904131f8cf6a36ce40b8b0c9c5da3
Patch-mainline: v5.7-rc1
References: git-fixes

pageno is an int and the PAGE_SHIFT shift is done on an int,
overflowing if the memory is bigger than 2G

This can be reproduced using for example a reserved-memory of 4G

reserved-memory {
		    #address-cells = <2>;
		    #size-cells = <2>;
		    ranges;

		    reserved_dma: buffer@0 {
		        compatible = "shared-dma-pool";
		        no-map;
		        reg = <0x5 0x00000000 0x1 0x0>;
        };
};

Signed-off-by: Kevin Grandemange <kevin.grandemange@allegrodvt.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 kernel/dma/coherent.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/kernel/dma/coherent.c b/kernel/dma/coherent.c
index 551b0eb7028a..2a0c4985f38e 100644
--- a/kernel/dma/coherent.c
+++ b/kernel/dma/coherent.c
@@ -134,7 +134,7 @@ static void *__dma_alloc_from_coherent(struct device *dev,
 
 	spin_lock_irqsave(&mem->spinlock, flags);
 
-	if (unlikely(size > (mem->size << PAGE_SHIFT)))
+	if (unlikely(size > ((dma_addr_t)mem->size << PAGE_SHIFT)))
 		goto err;
 
 	pageno = bitmap_find_free_region(mem->bitmap, mem->size, order);
@@ -144,8 +144,9 @@ static void *__dma_alloc_from_coherent(struct device *dev,
 	/*
 	 * Memory was found in the coherent area.
 	 */
-	*dma_handle = dma_get_device_base(dev, mem) + (pageno << PAGE_SHIFT);
-	ret = mem->virt_base + (pageno << PAGE_SHIFT);
+	*dma_handle = dma_get_device_base(dev, mem) +
+			((dma_addr_t)pageno << PAGE_SHIFT);
+	ret = mem->virt_base + ((dma_addr_t)pageno << PAGE_SHIFT);
 	spin_unlock_irqrestore(&mem->spinlock, flags);
 	memset(ret, 0, size);
 	return ret;
@@ -194,7 +195,7 @@ static int __dma_release_from_coherent(struct dma_coherent_mem *mem,
 				       int order, void *vaddr)
 {
 	if (mem && vaddr >= mem->virt_base && vaddr <
-		   (mem->virt_base + (mem->size << PAGE_SHIFT))) {
+		   (mem->virt_base + ((dma_addr_t)mem->size << PAGE_SHIFT))) {
 		int page = (vaddr - mem->virt_base) >> PAGE_SHIFT;
 		unsigned long flags;
 
@@ -238,10 +239,10 @@ static int __dma_mmap_from_coherent(struct dma_coherent_mem *mem,
 		struct vm_area_struct *vma, void *vaddr, size_t size, int *ret)
 {
 	if (mem && vaddr >= mem->virt_base && vaddr + size <=
-		   (mem->virt_base + (mem->size << PAGE_SHIFT))) {
+		   (mem->virt_base + ((dma_addr_t)mem->size << PAGE_SHIFT))) {
 		unsigned long off = vma->vm_pgoff;
 		int start = (vaddr - mem->virt_base) >> PAGE_SHIFT;
-		int user_count = vma_pages(vma);
+		unsigned long user_count = vma_pages(vma);
 		int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 
 		*ret = -ENXIO;
-- 
2.16.4