crypto: lib/mpi - Fix unexpected pointer access in mpi_ec_init

When the mpi_ec_ctx structure is initialized, some fields are not
cleared, causing a crash when referencing the field when the
structure was released. Initially, this issue was ignored because
memory for mpi_ec_ctx is allocated with the __GFP_ZERO flag.
For example, this error will be triggered when calculating the
Za value for SM2 separately.

Fixes: d58bb7e5 ("lib/mpi: Introduce ec implementation to MPI library")
Cc: stable@vger.kernel.org # v6.5
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

lib/crypto/mpi/ec.c

@@ -584,6 +584,9 @@ void mpi_ec_init(struct mpi_ec_ctx *ctx, enum gcry_mpi_ec_models model,
 	ctx->a = mpi_copy(a);
 	ctx->b = mpi_copy(b);
 
+	ctx->d = NULL;
+	ctx->t.two_inv_p = NULL;
+
 	ctx->t.p_barrett = use_barrett > 0 ? mpi_barrett_init(ctx->p, 0) : NULL;
 
 	mpi_ec_get_reset(ctx);