| Message ID | 20200909102640.1657622-3-warthog618@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | gpio: cdev: add uAPI v2 | expand |
On Wed, Sep 9, 2020 at 1:34 PM Kent Gibson <warthog618@gmail.com> wrote: > > Replace usage of strncpy with strscpy to remove -Wstringop-truncation strnspy() with strscpy() > warnings. > > The structs being populated are zeroed, to prevent stack leakage as structures > they are returned to userspace, so strscpy performs the equivalent strscpy() > function without the warnings. Isn't this what I commented on like half a year ago and back then reply was something that there is no warnings or so? Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> > Reported-by: kernel test robot <lkp@intel.com> > Signed-off-by: Kent Gibson <warthog618@gmail.com> > --- > > The memset in gpio_desc_to_lineinfo(), in conjunction with the strscpy, > is necessary as strncpy zero pads the remainder of the destination. > It also guarantees that the info cannot leak kernel stack to userspace. > This is useful here, but is even more important for the v2 info, that > this function is changed to generate in a subsequent patch, as that > struct contains padding and attribute arrays that also need to be > initialised. > > drivers/gpio/gpiolib-cdev.c | 23 +++++++---------------- > 1 file changed, 7 insertions(+), 16 deletions(-) > > diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c > index e95e3eab9867..8b012879fe3f 100644 > --- a/drivers/gpio/gpiolib-cdev.c > +++ b/drivers/gpio/gpiolib-cdev.c > @@ -752,6 +752,7 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc, > bool ok_for_pinctrl; > unsigned long flags; > > + memset(info, 0, sizeof(*info)); > info->line_offset = gpio_chip_hwgpio(desc); > /* > * This function takes a mutex so we must check this before taking > @@ -765,19 +766,11 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc, > > spin_lock_irqsave(&gpio_lock, flags); > > - if (desc->name) { > - strncpy(info->name, desc->name, sizeof(info->name)); > - info->name[sizeof(info->name) - 1] = '\0'; > - } else { > - info->name[0] = '\0'; > - } > + if (desc->name) > + strscpy(info->name, desc->name, sizeof(info->name)); > > - if (desc->label) { > - strncpy(info->consumer, desc->label, sizeof(info->consumer)); > - info->consumer[sizeof(info->consumer) - 1] = '\0'; > - } else { > - info->consumer[0] = '\0'; > - } > + if (desc->label) > + strscpy(info->consumer, desc->label, sizeof(info->consumer)); > > /* > * Userspace only need to know that the kernel is using this GPIO so > @@ -841,12 +834,10 @@ static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg) > > memset(&chipinfo, 0, sizeof(chipinfo)); > > - strncpy(chipinfo.name, dev_name(&gdev->dev), > + strscpy(chipinfo.name, dev_name(&gdev->dev), > sizeof(chipinfo.name)); > - chipinfo.name[sizeof(chipinfo.name)-1] = '\0'; > - strncpy(chipinfo.label, gdev->label, > + strscpy(chipinfo.label, gdev->label, > sizeof(chipinfo.label)); > - chipinfo.label[sizeof(chipinfo.label)-1] = '\0'; > chipinfo.lines = gdev->ngpio; > if (copy_to_user(ip, &chipinfo, sizeof(chipinfo))) > return -EFAULT; > -- > 2.28.0 >
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c index e95e3eab9867..8b012879fe3f 100644 --- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -752,6 +752,7 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc, bool ok_for_pinctrl; unsigned long flags; + memset(info, 0, sizeof(*info)); info->line_offset = gpio_chip_hwgpio(desc); /* * This function takes a mutex so we must check this before taking @@ -765,19 +766,11 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc, spin_lock_irqsave(&gpio_lock, flags); - if (desc->name) { - strncpy(info->name, desc->name, sizeof(info->name)); - info->name[sizeof(info->name) - 1] = '\0'; - } else { - info->name[0] = '\0'; - } + if (desc->name) + strscpy(info->name, desc->name, sizeof(info->name)); - if (desc->label) { - strncpy(info->consumer, desc->label, sizeof(info->consumer)); - info->consumer[sizeof(info->consumer) - 1] = '\0'; - } else { - info->consumer[0] = '\0'; - } + if (desc->label) + strscpy(info->consumer, desc->label, sizeof(info->consumer)); /* * Userspace only need to know that the kernel is using this GPIO so @@ -841,12 +834,10 @@ static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg) memset(&chipinfo, 0, sizeof(chipinfo)); - strncpy(chipinfo.name, dev_name(&gdev->dev), + strscpy(chipinfo.name, dev_name(&gdev->dev), sizeof(chipinfo.name)); - chipinfo.name[sizeof(chipinfo.name)-1] = '\0'; - strncpy(chipinfo.label, gdev->label, + strscpy(chipinfo.label, gdev->label, sizeof(chipinfo.label)); - chipinfo.label[sizeof(chipinfo.label)-1] = '\0'; chipinfo.lines = gdev->ngpio; if (copy_to_user(ip, &chipinfo, sizeof(chipinfo))) return -EFAULT;
Replace usage of strncpy with strscpy to remove -Wstringop-truncation warnings. The structs being populated are zeroed, to prevent stack leakage as they are returned to userspace, so strscpy performs the equivalent function without the warnings. Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Kent Gibson <warthog618@gmail.com> --- The memset in gpio_desc_to_lineinfo(), in conjunction with the strscpy, is necessary as strncpy zero pads the remainder of the destination. It also guarantees that the info cannot leak kernel stack to userspace. This is useful here, but is even more important for the v2 info, that this function is changed to generate in a subsequent patch, as that struct contains padding and attribute arrays that also need to be initialised. drivers/gpio/gpiolib-cdev.c | 23 +++++++---------------- 1 file changed, 7 insertions(+), 16 deletions(-)