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Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH v4 08/23] ata: libahci_platform: Sanity check the DT child nodes number Content-Language: en-US To: Serge Semin Cc: Serge Semin , Hans de Goede , Jens Axboe , Hannes Reinecke , Alexey Malahov , Pavel Parkhomenko , Rob Herring , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org References: <20220610081801.11854-1-Sergey.Semin@baikalelectronics.ru> <20220610081801.11854-9-Sergey.Semin@baikalelectronics.ru> <20220615205328.chwruabvksdbnaex@mobilestation> From: Damien Le Moal Organization: Western Digital Research In-Reply-To: <20220615205328.chwruabvksdbnaex@mobilestation> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 2022/06/16 5:53, Serge Semin wrote: > On Tue, Jun 14, 2022 at 05:23:33PM +0900, Damien Le Moal wrote: >> On 6/10/22 17:17, Serge Semin wrote: >>> Having greater than AHCI_MAX_PORTS (32) ports detected isn't that critical >>> from the further AHCI-platform initialization point of view since >>> exceeding the ports upper limit will cause allocating more resources than >>> will be used afterwards. But detecting too many child DT-nodes doesn't >>> seem right since it's very unlikely to have it on an ordinary platform. In >>> accordance with the AHCI specification there can't be more than 32 ports >>> implemented at least due to having the CAP.NP field of 5 bits wide and the >>> PI register of dword size. Thus if such situation is found the DTB must >>> have been corrupted and the data read from it shouldn't be reliable. Let's >>> consider that as an erroneous situation and halt further resources >>> allocation. >>> >>> Note it's logically more correct to have the nports set only after the >>> initialization value is checked for being sane. So while at it let's make >>> sure nports is assigned with a correct value. >>> >>> Signed-off-by: Serge Semin >>> Reviewed-by: Hannes Reinecke >>> >>> --- >>> >>> Changelog v2: >>> - Drop the else word from the child_nodes value checking if-else-if >>> statement (@Damien) and convert the after-else part into the ternary >>> operator-based statement. >>> >>> Changelog v4: >>> - Fix some logical mistakes in the patch log. (@Sergei Shtylyov) >>> --- >>> drivers/ata/libahci_platform.c | 13 ++++++++++--- >>> 1 file changed, 10 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c >>> index 814804582d1d..8aed7b29c7ab 100644 >>> --- a/drivers/ata/libahci_platform.c >>> +++ b/drivers/ata/libahci_platform.c >>> @@ -451,15 +451,22 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev, >>> } >>> } >>> >>> - hpriv->nports = child_nodes = of_get_child_count(dev->of_node); >>> + /* >>> + * Too many sub-nodes most likely means having something wrong with >>> + * the firmware. >>> + */ >>> + child_nodes = of_get_child_count(dev->of_node); >>> + if (child_nodes > AHCI_MAX_PORTS) { >>> + rc = -EINVAL; >>> + goto err_out; >>> + } >>> >>> /* >>> * If no sub-node was found, we still need to set nports to >>> * one in order to be able to use the >>> * ahci_platform_[en|dis]able_[phys|regulators] functions. >>> */ >>> - if (!child_nodes) >>> - hpriv->nports = 1; >>> + hpriv->nports = child_nodes ?: 1; >> > >> This change is not necessary and makes the code far less easy to read. > > elaborate please. What change? What part of this change makes the code > less easy to read? You changed: if (!child_nodes) hpriv->nports = 1; to: hpriv->nports = child_nodes ?: 1; That is the same. So the change is not needed in the first place, and worse, makes the code way harder to read for no good reason. > > -Sergey > >> >>> >>> hpriv->phys = devm_kcalloc(dev, hpriv->nports, sizeof(*hpriv->phys), GFP_KERNEL); >>> if (!hpriv->phys) { >> >> >> -- >> Damien Le Moal >> Western Digital Research -- Damien Le Moal Western Digital Research