Date: Thu, 22 Mar 2018 14:43:39 -0700 From: Laura Abbott <labbott@...hat.com> To: Phil Reid <preid@...ctromag.com.au>, Linus Walleij <linus.walleij@...aro.org>, Kees Cook <keescook@...omium.org>, Patrice Chotard <patrice.chotard@...com> Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com Subject: Re: [PATCHv2 4/4] gpio: Remove VLA from stmpe driver On 03/18/2018 06:29 PM, Phil Reid wrote: > On 16/03/2018 02:00, Laura Abbott wrote: >> The new challenge is to remove VLAs from the kernel >> (see https://lkml.org/lkml/2018/3/7/621) >> >> This patch replaces a VLA with an appropriate call to kmalloc_array. >> >> Signed-off-by: Laura Abbott <labbott@...hat.com> >> --- >> v2: Switch to GFP_KERNEL. There was some discussion about if we should >> be doing the allocation at all but given a) the allocation is pretty >> small and b) we can possibly take a mutex in a called function I think >> this is fine. > > I still think it's a bad idea. It's simple to preallocate the buffer. > But it's up to the maintainer. > I'd feel a lot more confident about doing the global buffer with guidance from the maintainer. But looking at the platform data, the maximum number of GPIOs is 24, or 3 banks. Maybe we should just always stack allocate the maximum since it's fairly small. Thanks, Laura > >> --- >> drivers/gpio/gpio-stmpe.c | 7 ++++++- >> 1 file changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/gpio/gpio-stmpe.c b/drivers/gpio/gpio-stmpe.c >> index f8d7d1cd8488..c2bb20ace6f5 100644 >> --- a/drivers/gpio/gpio-stmpe.c >> +++ b/drivers/gpio/gpio-stmpe.c >> @@ -369,10 +369,14 @@ static irqreturn_t stmpe_gpio_irq(int irq, void *dev) >> struct stmpe *stmpe = stmpe_gpio->stmpe; >> u8 statmsbreg; >> int num_banks = DIV_ROUND_UP(stmpe->num_gpios, 8); >> - u8 status[num_banks]; >> + u8 *status; >> int ret; >> int i; >> + status = kmalloc_array(num_banks, sizeof(*status), GFP_KERNEL); >> + if (!status) >> + return IRQ_NONE; >> + >> /* >> * the stmpe_block_read() call below, imposes to set statmsbreg >> * with the register located at the lowest address. As STMPE1600 >> @@ -424,6 +428,7 @@ static irqreturn_t stmpe_gpio_irq(int irq, void *dev) >> } >> } >> + kfree(status); >> return IRQ_HANDLED; >> } >> > >
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