Date: Tue, 13 Mar 2018 18:16:51 -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: [PATCH 4/4] gpio: Remove VLA from stmpe driver On 03/13/2018 05:18 PM, Laura Abbott wrote: > On 03/13/2018 02:13 AM, Phil Reid wrote: >> On 10/03/2018 08:10, 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> >>> --- >>> 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..b7854850bcdb 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_ATOMIC); >>> + 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; >>> } >>> >> >> Doing this in an irq handler seems wrong. >> Perhaps better if a buffer is pre-allocated in stmpe_gpio >> >> > > Sure, I can pre-allocate the buffer in the probe. > > Thanks, > Laura Actually I wonder if there would be concurrency problems if we tried to pre-allocate a global buffer. But the IRQ handler calls stmpe_block_read which takes a mutex to sleep so I think doing the (small) kmalloc should be fine and I can change it to a GFP_KERNEL. Thanks, Laura
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