linux-kernel - [PATCH 5.4 016/260] soc: aspeed: p2a-ctrl: Fix boundary check for mmap

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Date:   Mon, 20 Sep 2021 18:40:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Iwona Winiarska <iwona.winiarska@...el.com>,
        Andrew Jeffery <andrew@...id.au>, Joel Stanley <joel@...id.au>,
        Joel Stanley <joel@....id.au>
Subject: [PATCH 5.4 016/260] soc: aspeed: p2a-ctrl: Fix boundary check for mmap

From: Iwona Winiarska <iwona.winiarska@...el.com>

commit 8b07e990fb254fcbaa919616ac77f981cb48c73d upstream.

The check mixes pages (vm_pgoff) with bytes (vm_start, vm_end) on one
side of the comparison, and uses resource address (rather than just the
resource size) on the other side of the comparison.
This can allow malicious userspace to easily bypass the boundary check and
map pages that are located outside memory-region reserved by the driver.

Fixes: 01c60dcea9f7 ("drivers/misc: Add Aspeed P2A control driver")
Cc: stable@...r.kernel.org
Signed-off-by: Iwona Winiarska <iwona.winiarska@...el.com>
Reviewed-by: Andrew Jeffery <andrew@...id.au>
Tested-by: Andrew Jeffery <andrew@...id.au>
Reviewed-by: Joel Stanley <joel@...id.au>
Signed-off-by: Joel Stanley <joel@....id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/soc/aspeed/aspeed-p2a-ctrl.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/soc/aspeed/aspeed-p2a-ctrl.c
+++ b/drivers/soc/aspeed/aspeed-p2a-ctrl.c
@@ -110,7 +110,7 @@ static int aspeed_p2a_mmap(struct file *
 	vsize = vma->vm_end - vma->vm_start;
 	prot = vma->vm_page_prot;
 
-	if (vma->vm_pgoff + vsize > ctrl->mem_base + ctrl->mem_size)
+	if (vma->vm_pgoff + vma_pages(vma) > ctrl->mem_size >> PAGE_SHIFT)
 		return -EINVAL;
 
 	/* ast2400/2500 AHB accesses are not cache coherent */