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    SubjectRe: [PATCH] drbd: dynamically allocate shash descriptor
    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 <arnd@arndb.de>
    > ---
    > drivers/block/drbd/drbd_receiver.c | 10 +++++++++-
    > 1 file changed, 9 insertions(+), 1 deletion(-)

    Does this patch fix the warning as well?

    diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
    index 90ebfcae0ce6..ead13a6b3887 100644
    --- a/drivers/block/drbd/drbd_receiver.c
    +++ b/drivers/block/drbd/drbd_receiver.c
    @@ -5401,6 +5401,35 @@ static int drbd_do_auth(struct drbd_connection *connection)
    #else
    #define CHALLENGE_LEN 64

    +static char *drbd_get_response(struct drbd_connection *connection,
    + const char *challenge, unsigned int len)
    +{
    + unsigned dlen = crypto_shash_digestsize(connection->cram_hmac_tfm);
    + SHASH_DESC_ON_STACK(desc, connection->cram_hmac_tfm);
    + char *response;
    + int err;
    +
    + desc->tfm = connection->cram_hmac_tfm;
    +
    + response = kmalloc(dlen, GFP_NOIO);
    + if (!response) {
    + drbd_err(connection, "kmalloc of response failed\n");
    + goto out;
    + }
    +
    + err = crypto_shash_digest(desc, challenge, len, response);
    + if (err) {
    + drbd_err(connection, "crypto_shash_digest() failed with %d\n",
    + err);
    + kfree(response);
    + response = NULL;
    + }
    +
    +out:
    + shash_desc_zero(desc);
    + return response;
    +}
    +
    /* Return value:
    1 - auth succeeded,
    0 - failed, try again (network error),
    @@ -5417,7 +5446,6 @@ 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 packet_info pi;
    struct net_conf *nc;
    int err, rv;
    @@ -5430,8 +5458,6 @@ static int drbd_do_auth(struct drbd_connection *connection)
    memcpy(secret, nc->shared_secret, key_len);
    rcu_read_unlock();

    - desc->tfm = connection->cram_hmac_tfm;
    -
    rv = crypto_shash_setkey(connection->cram_hmac_tfm, (u8 *)secret, key_len);
    if (rv) {
    drbd_err(connection, "crypto_shash_setkey() failed with %d\n", rv);
    @@ -5496,16 +5522,8 @@ static int drbd_do_auth(struct drbd_connection *connection)
    }

    resp_size = crypto_shash_digestsize(connection->cram_hmac_tfm);
    - response = kmalloc(resp_size, GFP_NOIO);
    + response = drbd_get_response(connection, peers_ch, pi.size);
    if (response == NULL) {
    - drbd_err(connection, "kmalloc of response failed\n");
    - rv = -1;
    - goto fail;
    - }
    -
    - rv = crypto_shash_digest(desc, peers_ch, pi.size, response);
    - if (rv) {
    - drbd_err(connection, "crypto_hash_digest() failed with %d\n", rv);
    rv = -1;
    goto fail;
    }
    @@ -5544,17 +5562,9 @@ static int drbd_do_auth(struct drbd_connection *connection)
    goto fail;
    }

    - right_response = kmalloc(resp_size, GFP_NOIO);
    + right_response = drbd_get_response(connection, my_challenge,
    + CHALLENGE_LEN);
    if (right_response == NULL) {
    - drbd_err(connection, "kmalloc of right_response failed\n");
    - rv = -1;
    - goto fail;
    - }
    -
    - rv = crypto_shash_digest(desc, my_challenge, CHALLENGE_LEN,
    - right_response);
    - if (rv) {
    - drbd_err(connection, "crypto_hash_digest() failed with %d\n", rv);
    rv = -1;
    goto fail;
    }
    @@ -5571,7 +5581,6 @@ static int drbd_do_auth(struct drbd_connection *connection)
    kfree(peers_ch);
    kfree(response);
    kfree(right_response);
    - shash_desc_zero(desc);

    return rv;
    }
    --
    Email: Herbert Xu <herbert@gondor.apana.org.au>
    Home Page: http://gondor.apana.org.au/~herbert/
    PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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