Re: [cip-dev] phy-rcar-gen3-usb2: wrong parsing of role in role_store?
From: Ben Hutchings
Date: Thu Aug 01 2019 - 14:51:11 EST
On Tue, 2019-07-30 at 11:51 +0200, Pavel Machek wrote:
> 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.
> 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;
> return -EINVAL;
> cip-dev mailing list
Ben Hutchings, Software Developer Codethink Ltd
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