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SubjectRe: [PATCH] EDAC, thunderx: Remove VLA usage
On Fri, Jun 29, 2018 at 11:48:50AM -0700, Kees Cook wrote:
> In the quest to remove all stack VLA usage from the kernel[1], this
> switches to using a kmalloc-allocated buffer instead of stack space.
> This should be fine since the existing routine is allocating memory
> too.
>
> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>
> Cc: David Daney <david.daney@cavium.com>
> Cc: Jan Glauber <jglauber@cavium.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: linux-edac@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Acked-by: Jan Glauber <jglauber@cavium.com>

thanks,
Jan

> ---
> drivers/edac/thunderx_edac.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/edac/thunderx_edac.c b/drivers/edac/thunderx_edac.c
> index 4803c6468bab..c009d94f40c5 100644
> --- a/drivers/edac/thunderx_edac.c
> +++ b/drivers/edac/thunderx_edac.c
> @@ -408,26 +408,29 @@ static ssize_t thunderx_lmc_inject_ecc_write(struct file *file,
> size_t count, loff_t *ppos)
> {
> struct thunderx_lmc *lmc = file->private_data;
> -
> unsigned int cline_size = cache_line_size();
> -
> - u8 tmp[cline_size];
> + u8 *tmp;
> void __iomem *addr;
> unsigned int offs, timeout = 100000;
>
> atomic_set(&lmc->ecc_int, 0);
>
> lmc->mem = alloc_pages_node(lmc->node, GFP_KERNEL, 0);
> -
> if (!lmc->mem)
> return -ENOMEM;
>
> + tmp = kmalloc(cline_size, GFP_KERNEL);
> + if (!tmp) {
> + __free_pages(lmc->mem, 0);
> + return -ENOMEM;
> + }
> +
> addr = page_address(lmc->mem);
>
> while (!atomic_read(&lmc->ecc_int) && timeout--) {
> stop_machine(inject_ecc_fn, lmc, NULL);
>
> - for (offs = 0; offs < PAGE_SIZE; offs += sizeof(tmp)) {
> + for (offs = 0; offs < PAGE_SIZE; offs += cline_size) {
> /*
> * Do a load from the previously rigged location
> * This should generate an error interrupt.
> @@ -437,6 +440,7 @@ static ssize_t thunderx_lmc_inject_ecc_write(struct file *file,
> }
> }
>
> + kfree(tmp);
> __free_pages(lmc->mem, 0);
>
> return count;
> --
> 2.17.1
>
>
> --
> Kees Cook
> Pixel Security

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