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[156.34.48.30]) by smtp.gmail.com with ESMTPSA id i35sm19119142qtd.96.2020.07.13.10.09.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Jul 2020 10:09:41 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.93) (envelope-from ) id 1jv1xV-009lWJ-4g; Mon, 13 Jul 2020 14:09:41 -0300 Date: Mon, 13 Jul 2020 14:09:41 -0300 From: Jason Gunthorpe To: "Saheed O. Bolarinwa" Cc: skhan@linuxfoundation.org, linux-rdma@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/14 v3] IB/hfi1: Check the return value of pcie_capability_read_*() Message-ID: <20200713170941.GB25301@ziepe.ca> References: <20200713175529.29715-1-refactormyself@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200713175529.29715-1-refactormyself@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 13, 2020 at 07:55:25PM +0200, Saheed O. Bolarinwa wrote: > From: Bolarinwa Olayemi Saheed > > On failure pcie_capability_read_dword() sets it's last parameter, > val to 0. In this case dn and up will be 0, so aspm_hw_l1_supported() > will return false. > However, with Patch 14/14, it is possible that val is set to ~0 on > failure. This would introduce a bug because (x & x) == (~0 & x). So with > dn and up being 0x02, a true value is return when the read has actually > failed. > > This bug can be avoided if the return value of pcie_capability_read_dword > is checked to confirm success. The behaviour of the function remains > intact. > > Check the return value of pcie_capability_read_dword() to ensure success. > > Suggested-by: Bjorn Helgaas > Signed-off-by: Bolarinwa Olayemi Saheed > drivers/infiniband/hw/hfi1/aspm.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/infiniband/hw/hfi1/aspm.c b/drivers/infiniband/hw/hfi1/aspm.c > index a3c53be4072c..80d0b3edd983 100644 > +++ b/drivers/infiniband/hw/hfi1/aspm.c > @@ -24,6 +24,7 @@ static bool aspm_hw_l1_supported(struct hfi1_devdata *dd) > { > struct pci_dev *parent = dd->pcidev->bus->self; > u32 up, dn; > + int ret_up, ret_dn; > > /* > * If the driver does not have access to the upstream component, > @@ -32,14 +33,14 @@ static bool aspm_hw_l1_supported(struct hfi1_devdata *dd) > if (!parent) > return false; > > - pcie_capability_read_dword(dd->pcidev, PCI_EXP_LNKCAP, &dn); > + ret_dn = pcie_capability_read_dword(dd->pcidev, PCI_EXP_LNKCAP, &dn); > dn = ASPM_L1_SUPPORTED(dn); > > - pcie_capability_read_dword(parent, PCI_EXP_LNKCAP, &up); > + ret_up = pcie_capability_read_dword(parent, PCI_EXP_LNKCAP, &up); > up = ASPM_L1_SUPPORTED(up); > > /* ASPM works on A-step but is reported as not supported */ > - return (!!dn || is_ax(dd)) && !!up; > + return !!ret_dn && !!ret_up && (!!dn || is_ax(dd)) && !!up; > } what is all the !! for? boolean contexts already coerce to boolean Jason