linux-kernel - [PATCH] char: amd64-agp: Use 64-bit arithmetic instead of 32-bit

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Date:   Wed, 4 Jul 2018 17:20:41 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     David Airlie <airlied@...ux.ie>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] char: amd64-agp: Use 64-bit arithmetic instead of 32-bit

Cast *tmp* and *nb_base* to u64 in order to give the compiler
complete information about the proper arithmetic to use.

Notice that such variables are used in contexts that expect
expressions of type u64 (64 bits, unsigned) and the following
expressions are currently being evaluated using 32-bit arithmetic:

tmp << 25
nb_base << 25

Addresses-Coverity-ID: 200586 ("Unintentional integer overflow")
Addresses-Coverity-ID: 200587 ("Unintentional integer overflow")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/char/agp/amd64-agp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/char/agp/amd64-agp.c b/drivers/char/agp/amd64-agp.c
index e50c29c..c69e39f 100644
--- a/drivers/char/agp/amd64-agp.c
+++ b/drivers/char/agp/amd64-agp.c
@@ -156,7 +156,7 @@ static u64 amd64_configure(struct pci_dev *hammer, u64 gatt_table)
 
 	/* Address to map to */
 	pci_read_config_dword(hammer, AMD64_GARTAPERTUREBASE, &tmp);
-	aperturebase = tmp << 25;
+	aperturebase = (u64)tmp << 25;
 	aper_base = (aperturebase & PCI_BASE_ADDRESS_MEM_MASK);
 
 	enable_gart_translation(hammer, gatt_table);
@@ -277,7 +277,7 @@ static int fix_northbridge(struct pci_dev *nb, struct pci_dev *agp, u16 cap)
 	pci_read_config_dword(nb, AMD64_GARTAPERTURECTL, &nb_order);
 	nb_order = (nb_order >> 1) & 7;
 	pci_read_config_dword(nb, AMD64_GARTAPERTUREBASE, &nb_base);
-	nb_aper = nb_base << 25;
+	nb_aper = (u64)nb_base << 25;
 
 	/* Northbridge seems to contain crap. Try the AGP bridge. */
 
-- 
2.7.4