On Mon, Jun 17, 2019 at 03:24:13PM +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.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> drivers/block/drbd/drbd_receiver.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/block/drbd/drbd_receiver.c
> b/drivers/block/drbd/drbd_receiver.c
> index 90ebfcae0ce6..10fb26e862d7 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);
> @@ -5572,6 +5579,7 @@ static int drbd_do_auth(struct drbd_connection
> *connection)
> kfree(response);
> kfree(right_response);
> shash_desc_zero(desc);
> + kfree(desc);
>
> return rv;
> }
Hi Arnd,
are you sure your cleanup is okay?
> shash_desc_zero(desc);
> + kfree(desc);
You shash_desc_zero() a potential NULL pointer. memzero_expicit() in the
function then dereferences it:
memzero_explicit(desc,
sizeof(*desc) + crypto_shash_descsize(desc->tfm));
Maybe some if (desc) guard?
Best, rck
