| Message ID | 20180529225901.GA30464@beast |
|---|---|
| State | New |
| Headers | show |
| Series | mdio-mux-gpio: Remove VLA usage | expand |
On Tue, 2018-05-29 at 15:59 -0700, Kees Cook wrote: > In the quest to remove all stack VLA usage from the kernel[1], this > allocates the values buffer during the callback instead of putting it > on the stack. > > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com [] > diff --git a/drivers/net/phy/mdio-mux-gpio.c b/drivers/net/phy/mdio-mux-gpio.c [] > @@ -26,18 +26,23 @@ static int mdio_mux_gpio_switch_fn(int current_child, int desired_child, > void *data) > { > struct mdio_mux_gpio_state *s = data; > - int values[s->gpios->ndescs]; > + int *values; > unsigned int n; > > if (current_child == desired_child) > return 0; > > + values = kmalloc_array(s->gpios->ndescs, sizeof(*values), GFP_KERNEL); > + if (!values) > + return -ENOMEM; This function previously only returned 0 and now it can return -ENOMEM. How do you know all the indirect callers via the switch_fn stored in mdio_mux_init can handle the new return value? If you have explored these code paths, it would be good to explain that in the commit message. -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, May 29, 2018 at 03:59:01PM -0700, Kees Cook wrote: > In the quest to remove all stack VLA usage from the kernel[1], this > allocates the values buffer during the callback instead of putting it > on the stack. > > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > drivers/net/phy/mdio-mux-gpio.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/phy/mdio-mux-gpio.c b/drivers/net/phy/mdio-mux-gpio.c > index 082ffef0dec4..e99994f4ed50 100644 > --- a/drivers/net/phy/mdio-mux-gpio.c > +++ b/drivers/net/phy/mdio-mux-gpio.c > @@ -26,18 +26,23 @@ static int mdio_mux_gpio_switch_fn(int current_child, int desired_child, > void *data) > { > struct mdio_mux_gpio_state *s = data; > - int values[s->gpios->ndescs]; > + int *values; > unsigned int n; > > if (current_child == desired_child) > return 0; > > + values = kmalloc_array(s->gpios->ndescs, sizeof(*values), GFP_KERNEL); > + if (!values) > + return -ENOMEM; > + > for (n = 0; n < s->gpios->ndescs; n++) > values[n] = (desired_child >> n) & 1; > > gpiod_set_array_value_cansleep(s->gpios->ndescs, s->gpios->desc, > values); > > + kfree(values); > return 0; > } Hi Kees This is the 'hot path' for this driver, and you are making it more expensive. Please allocate the memory once in mdio_mux_gpio_probe and make it part of mdio_mux_gpio_state. Thanks Andrew -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/net/phy/mdio-mux-gpio.c b/drivers/net/phy/mdio-mux-gpio.c index 082ffef0dec4..e99994f4ed50 100644 --- a/drivers/net/phy/mdio-mux-gpio.c +++ b/drivers/net/phy/mdio-mux-gpio.c @@ -26,18 +26,23 @@ static int mdio_mux_gpio_switch_fn(int current_child, int desired_child, void *data) { struct mdio_mux_gpio_state *s = data; - int values[s->gpios->ndescs]; + int *values; unsigned int n; if (current_child == desired_child) return 0; + values = kmalloc_array(s->gpios->ndescs, sizeof(*values), GFP_KERNEL); + if (!values) + return -ENOMEM; + for (n = 0; n < s->gpios->ndescs; n++) values[n] = (desired_child >> n) & 1; gpiod_set_array_value_cansleep(s->gpios->ndescs, s->gpios->desc, values); + kfree(values); return 0; }
In the quest to remove all stack VLA usage from the kernel[1], this allocates the values buffer during the callback instead of putting it on the stack. [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook <keescook@chromium.org> --- drivers/net/phy/mdio-mux-gpio.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)