linux-kernel - [PATCH 3.16 03/99] x86/PCI: Fix Broadcom CNB20LE unintended sign extension (redux)

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Message-ID: <lsq.1554212307.749530593@decadent.org.uk>
Date:   Tue, 02 Apr 2019 14:38:27 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Bjorn Helgaas" <helgaas@...nel.org>,
        "Colin Ian King" <colin.king@...onical.com>
Subject: [PATCH 3.16 03/99] x86/PCI: Fix Broadcom CNB20LE unintended sign
 extension (redux)

3.16.65-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Colin Ian King <colin.king@...onical.com>

commit 53bb565fc5439f2c8c57a786feea5946804aa3e9 upstream.

In the expression "word1 << 16", word1 starts as u16, but is promoted to a
signed int, then sign-extended to resource_size_t, which is probably not
what was intended.  Cast to resource_size_t to avoid the sign extension.

This fixes an identical issue as fixed by commit 0b2d70764bb3 ("x86/PCI:
Fix Broadcom CNB20LE unintended sign extension") back in 2014.

Detected by CoverityScan, CID#138749, 138750 ("Unintended sign extension")

Fixes: 3f6ea84a3035 ("PCI: read memory ranges out of Broadcom CNB20LE host bridge")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
Signed-off-by: Bjorn Helgaas <helgaas@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/pci/broadcom_bus.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/pci/broadcom_bus.c
+++ b/arch/x86/pci/broadcom_bus.c
@@ -50,8 +50,8 @@ static void __init cnb20le_res(u8 bus, u
 	word1 = read_pci_config_16(bus, slot, func, 0xc0);
 	word2 = read_pci_config_16(bus, slot, func, 0xc2);
 	if (word1 != word2) {
-		res.start = (word1 << 16) | 0x0000;
-		res.end   = (word2 << 16) | 0xffff;
+		res.start = ((resource_size_t) word1 << 16) | 0x0000;
+		res.end   = ((resource_size_t) word2 << 16) | 0xffff;
 		res.flags = IORESOURCE_MEM;
 		update_res(info, res.start, res.end, res.flags, 0);
 	}