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

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Date:   Thu, 25 Oct 2018 14:52:31 +0100
From:   Colin King <colin.king@...onical.com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-pci@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] x86/PCI: Fix Broadcom CNB20LE unintended sign extension (redux)

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

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>
---
 arch/x86/pci/broadcom_bus.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/pci/broadcom_bus.c b/arch/x86/pci/broadcom_bus.c
index 526536c81ddc..d09c401a300d 100644
--- 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, u8 slot, u8 func)
 	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);
 	}
-- 
2.19.1