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SubjectRe: [PATCH] [v2] drbd: dynamically allocate shash descriptor
On Mon, Jul 22, 2019 at 02:26:34PM +0200, Arnd Bergmann wrote:
> Building with clang and KASAN, we get a warning about an overly large
> stack frame on 32-bit architectures:
>
> drivers/block/drbd/drbd_receiver.c:921:31: error: stack frame size of 1280 bytes in function 'conn_connect'
> [-Werror,-Wframe-larger-than=]
>
> We already allocate other data dynamically in this function, so
> just do the same for the shash descriptor, which makes up most of
> this memory.
>
> Link: https://lore.kernel.org/lkml/20190617132440.2721536-1-arnd@arndb.de/
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
> v2:
> - don't try to zero a NULL descriptor pointer,
> based on review from Roland Kammerer.
> ---
> drivers/block/drbd/drbd_receiver.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
> index 90ebfcae0ce6..2b3103c30857 100644
> --- a/drivers/block/drbd/drbd_receiver.c
> +++ b/drivers/block/drbd/drbd_receiver.c
> @@ -5417,7 +5417,7 @@ static int drbd_do_auth(struct drbd_connection *connection)
> unsigned int key_len;
> char secret[SHARED_SECRET_MAX]; /* 64 byte */
> unsigned int resp_size;
> - SHASH_DESC_ON_STACK(desc, connection->cram_hmac_tfm);
> + struct shash_desc *desc;
> struct packet_info pi;
> struct net_conf *nc;
> int err, rv;
> @@ -5430,6 +5430,13 @@ static int drbd_do_auth(struct drbd_connection *connection)
> memcpy(secret, nc->shared_secret, key_len);
> rcu_read_unlock();
>
> + desc = kmalloc(sizeof(struct shash_desc) +
> + crypto_shash_descsize(connection->cram_hmac_tfm),
> + GFP_KERNEL);
> + if (!desc) {
> + rv = -1;
> + goto fail;
> + }
> desc->tfm = connection->cram_hmac_tfm;
>
> rv = crypto_shash_setkey(connection->cram_hmac_tfm, (u8 *)secret, key_len);
> @@ -5571,7 +5578,10 @@ static int drbd_do_auth(struct drbd_connection *connection)
> kfree(peers_ch);
> kfree(response);
> kfree(right_response);
> - shash_desc_zero(desc);
> + if (desc) {
> + shash_desc_zero(desc);
> + kfree(desc);
> + }
>
> return rv;
> }
> --
> 2.20.0
>

--
Kees Cook

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