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Message-ID: <ffe639374bd93fe76f4aed19883640fefebd08f4.camel@codethink.co.uk>
Date: Thu, 01 Aug 2019 19:51:02 +0100
From: Ben Hutchings <ben.hutchings@...ethink.co.uk>
To: Pavel Machek <pavel@...x.de>, yoshihiro.shimoda.uh@...esas.com,
kishon@...com, linux-renesas-soc@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: cip-dev@...ts.cip-project.org
Subject: Re: [cip-dev] phy-rcar-gen3-usb2: wrong parsing of role in
role_store?
On Tue, 2019-07-30 at 11:51 +0200, Pavel Machek wrote:
> Hi!
>
> Code does strcmps, but does not actually check count. So AFAICT
> writing "host-I-don't-want-I-need-peripheral" into the file will
> succeed and turn it into host mode.
I suspect the intent is to work without a trailing "\n", but you're
right that this parsing is rather lax.
> Also data beyond count in buf are going to be accessed.
All attribute writes should be going through kernfs_fop_write(), which
writes a null terminator at buf[count] before calling the write/store
function. (I don't know where that'ss documented though.) So I think
this is safe.
Ben.
> static ssize_t role_store(struct device *dev, struct device_attribute *attr,
> const char *buf, size_t count)
> {
> struct rcar_gen3_chan *ch = dev_get_drvdata(dev);
> bool is_b_device;
> enum phy_mode cur_mode, new_mode;
>
> if (!ch->is_otg_channel || !rcar_gen3_is_any_rphy_initialized(ch))
> return -EIO;
>
> /* FIXME, this is wrong */
> if (!strncmp(buf, "host", strlen("host")))
> new_mode = PHY_MODE_USB_HOST;
> else if (!strncmp(buf, "peripheral", strlen("peripheral")))
> new_mode = PHY_MODE_USB_DEVICE;
> else
> return -EINVAL;
>
>
> _______________________________________________
> cip-dev mailing list
> cip-dev@...ts.cip-project.org
> https://lists.cip-project.org/mailman/listinfo/cip-dev
--
Ben Hutchings, Software Developer Codethink Ltd
https://www.codethink.co.uk/ Dale House, 35 Dale Street
Manchester, M1 2HF, United Kingdom
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