From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f49.google.com ([209.85.220.49]:52440 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753021AbaDDPk1 (ORCPT ); Fri, 4 Apr 2014 11:40:27 -0400 Received: by mail-pa0-f49.google.com with SMTP id lj1so3617650pab.36 for ; Fri, 04 Apr 2014 08:40:26 -0700 (PDT) Date: Fri, 4 Apr 2014 09:40:23 -0600 From: Bjorn Helgaas To: "Ira W. Snyder" Cc: Yinghai Lu , "linux-pci@vger.kernel.org" Subject: Re: Coverity CIDs 138749, 138750: cnb20le_res() unintended sign extension Message-ID: <20140404154023.GA5367@google.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-pci-owner@vger.kernel.org List-ID: On Thu, Apr 03, 2014 at 02:56:26PM -0600, Bjorn Helgaas wrote: > Coverity complains about unintended sign extension in cnb20le_res() in > arch/x86/pci/broadcom_bus.c here: > > 60 word1 = read_pci_config_16(bus, slot, func, 0xc4); > 61 word2 = read_pci_config_16(bus, slot, func, 0xc6); > 62 if (word1 != word2) { > > CID 138749 (#1 of 2): Unintended sign extension (SIGN_EXTENSION) > sign_extension: Suspicious implicit sign extension: word1 with type > unsigned short (16 bits, unsigned) is promoted in (word1 << 16) | 0 to > type int (32 bits, signed), then sign-extended to type unsigned long > long (64 bits, unsigned). If (word1 << 16) | 0 is greater than > 0x7FFFFFFF, the upper bits of the result will all be 1. > 63 res.start = (word1 << 16) | 0x0000; > CID 138750: Unintended sign extension (SIGN_EXTENSION) [select issue] I propose the following patch for this. Unless there's objection, I'll queue this for v3.16. x86/PCI: Fix Broadcom CNB20LE unintended sign extension From: Bjorn Helgaas 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. Found by Coverity (CID 138749, 138750). Signed-off-by: Bjorn Helgaas --- 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 614392ced7d6..bb461cfd01ab 100644 --- a/arch/x86/pci/broadcom_bus.c +++ b/arch/x86/pci/broadcom_bus.c @@ -60,8 +60,8 @@ static void __init cnb20le_res(u8 bus, u8 slot, u8 func) word1 = read_pci_config_16(bus, slot, func, 0xc4); word2 = read_pci_config_16(bus, slot, func, 0xc6); 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 | IORESOURCE_PREFETCH; update_res(info, res.start, res.end, res.flags, 0); }