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SubjectRe: [PATCH v2] mtd: nftl: Remove VLA usage
On Sun, 29 Apr 2018 08:00:53 -0700
Kees Cook <keescook@chromium.org> wrote:

> On the quest to remove all stack VLAs from the kernel[1] this changes
> the check_free_sectors() routine to use a kmalloc()ed buffer instead
> of a large VLA stack buffer.
>
> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>
> Signed-off-by: Kees Cook <keescook@chromium.org>

Applied to mtd/next.

Thanks,

Boris

> ---
> v2: kmalloc() instead of stack buffer (Boris)
> ---
> drivers/mtd/inftlmount.c | 23 ++++++++++++++++-------
> drivers/mtd/nftlmount.c | 23 ++++++++++++++++-------
> 2 files changed, 32 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/mtd/inftlmount.c b/drivers/mtd/inftlmount.c
> index aab4f68bd36f..2d598412972d 100644
> --- a/drivers/mtd/inftlmount.c
> +++ b/drivers/mtd/inftlmount.c
> @@ -334,28 +334,37 @@ static int memcmpb(void *a, int c, int n)
> static int check_free_sectors(struct INFTLrecord *inftl, unsigned int address,
> int len, int check_oob)
> {
> - u8 buf[SECTORSIZE + inftl->mbd.mtd->oobsize];
> struct mtd_info *mtd = inftl->mbd.mtd;
> size_t retlen;
> - int i;
> + int i, ret;
> + u8 *buf;
> +
> + buf = kmalloc(SECTORSIZE + mtd->oobsize, GFP_KERNEL);
> + if (!buf)
> + return -1;
>
> + ret = -1;
> for (i = 0; i < len; i += SECTORSIZE) {
> if (mtd_read(mtd, address, SECTORSIZE, &retlen, buf))
> - return -1;
> + goto out;
> if (memcmpb(buf, 0xff, SECTORSIZE) != 0)
> - return -1;
> + goto out;
>
> if (check_oob) {
> if(inftl_read_oob(mtd, address, mtd->oobsize,
> &retlen, &buf[SECTORSIZE]) < 0)
> - return -1;
> + goto out;
> if (memcmpb(buf + SECTORSIZE, 0xff, mtd->oobsize) != 0)
> - return -1;
> + goto out;
> }
> address += SECTORSIZE;
> }
>
> - return 0;
> + ret = 0;
> +
> +out:
> + kfree(buf);
> + return ret;
> }
>
> /*
> diff --git a/drivers/mtd/nftlmount.c b/drivers/mtd/nftlmount.c
> index a6fbfa4e5799..6281da3dadac 100644
> --- a/drivers/mtd/nftlmount.c
> +++ b/drivers/mtd/nftlmount.c
> @@ -272,28 +272,37 @@ static int memcmpb(void *a, int c, int n)
> static int check_free_sectors(struct NFTLrecord *nftl, unsigned int address, int len,
> int check_oob)
> {
> - u8 buf[SECTORSIZE + nftl->mbd.mtd->oobsize];
> struct mtd_info *mtd = nftl->mbd.mtd;
> size_t retlen;
> - int i;
> + int i, ret;
> + u8 *buf;
> +
> + buf = kmalloc(SECTORSIZE + mtd->oobsize, GFP_KERNEL);
> + if (!buf)
> + return -1;
>
> + ret = -1;
> for (i = 0; i < len; i += SECTORSIZE) {
> if (mtd_read(mtd, address, SECTORSIZE, &retlen, buf))
> - return -1;
> + goto out;
> if (memcmpb(buf, 0xff, SECTORSIZE) != 0)
> - return -1;
> + goto out;
>
> if (check_oob) {
> if(nftl_read_oob(mtd, address, mtd->oobsize,
> &retlen, &buf[SECTORSIZE]) < 0)
> - return -1;
> + goto out;
> if (memcmpb(buf + SECTORSIZE, 0xff, mtd->oobsize) != 0)
> - return -1;
> + goto out;
> }
> address += SECTORSIZE;
> }
>
> - return 0;
> + ret = 0;
> +
> +out:
> + kfree(buf);
> + return ret;
> }
>
> /* NFTL_format: format a Erase Unit by erasing ALL Erase Zones in the Erase Unit and

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