Re: [PATCH] HID: roccat: add bounds checking in kone_sysfs_write_settings()
From: Stefan Achatz <hidden>
Date: 2020-08-19 06:53:37
Also in:
kernel-janitors, lkml
Please remove the settings->size check. The driver sometimes just writes a modified version of the read settings data. This would fail if stored size is invalid. This value of size is not solely in my hands, I can't guarantee Windows driver does a sanity check, also cases of flash data corruption are known. My general design agenda is that in my userspace tools I make sure only valid data (to the best of knowledge) is prepared for the device. In the kernel driver I don't (or didn't) do additional checks and eventually let the hardware reject things it doesn't like. This way the kernel driver doesn't need an update if firmware updates change the binary interface. This happend in the past, but won't for this device anymore because it's oop for years. Am Mittwoch, den 05.08.2020, 12:55 +0300 schrieb Dan Carpenter:
quoted hunk ↗ jump to hunk
In the original code we didn't check if the new value for "settings->startup_profile" was within bounds that could possibly result in an out of bounds array acccess. What we did was we checked if we could write the data to the firmware and it's possibly the firmware checks these values but there is no way to know. It's safer and easier to read if we check it in the kernel as well. I also added a check to ensure that "settings->size" was correct. The comments say that the only valid value is 36 which is sizeof(struct kone_settings). Fixes: 14bf62cde794 ("HID: add driver for Roccat Kone gaming mouse") Signed-off-by: Dan Carpenter <redacted> --- This isn't tested. Checking settings->size seems like a good idea, but there is a slight risky because maybe invalid values used to be allowed and I don't want to break user space. drivers/hid/hid-roccat-kone.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-)diff --git a/drivers/hid/hid-roccat-kone.c b/drivers/hid/hid-roccat-kone.c index 1a6e600197d0..5e8e1517f23c 100644--- a/drivers/hid/hid-roccat-kone.c +++ b/drivers/hid/hid-roccat-kone.c@@ -294,31 +294,41 @@ static ssize_t kone_sysfs_write_settings(structfile *fp, struct kobject *kobj, struct kone_device *kone = hid_get_drvdata(dev_get_drvdata(dev)); struct usb_device *usb_dev = interface_to_usbdev(to_usb_interface(dev)); int retval = 0, difference, old_profile; + struct kone_settings *settings = (struct kone_settings *)buf; /* I need to get my data in one piece */ if (off != 0 || count != sizeof(struct kone_settings)) return -EINVAL; mutex_lock(&kone->kone_lock); - difference = memcmp(buf, &kone->settings, sizeof(struct kone_settings)); + difference = memcmp(settings, &kone->settings, + sizeof(struct kone_settings)); if (difference) { - retval = kone_set_settings(usb_dev, - (struct kone_settings const *)buf); - if (retval) { - mutex_unlock(&kone->kone_lock); - return retval; + if (settings->size != sizeof(struct kone_settings) || + settings->startup_profile < 1 || + settings->startup_profile > 5) { + retval = -EINVAL; + goto unlock; } + retval = kone_set_settings(usb_dev, settings); + if (retval) + goto unlock; + old_profile = kone->settings.startup_profile; - memcpy(&kone->settings, buf, sizeof(struct kone_settings)); + memcpy(&kone->settings, settings, sizeof(struct kone_settings)); kone_profile_activated(kone, kone-quoted
settings.startup_profile);if (kone->settings.startup_profile != old_profile) kone_profile_report(kone, kone-quoted
settings.startup_profile);} +unlock: mutex_unlock(&kone->kone_lock); + if (retval) + return retval; + return sizeof(struct kone_settings); } static BIN_ATTR(settings, 0660, kone_sysfs_read_settings,