ICP: Fix null pointer dereference and use after free

In gcm_mode_decrypt_contiguous_blocks(), if vmem_alloc() fails,
bcopy is called with a NULL pointer destination and a length > 0.
This results in undefined behavior. Further ctx->gcm_pt_buf is
freed but not set to NULL, leading to a potential write after
free and a double free due to missing return value handling in
crypto_update_uio(). The code as is may write to ctx->gcm_pt_buf
in gcm_decrypt_final() and may free ctx->gcm_pt_buf again in
aes_decrypt_atomic().

The fix is to slightly rework error handling and check the return
value in crypto_update_uio().

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tom Caputi <tcaputi@datto.com>
Reviewed-by: Kjeld Schouten <kjeld@schouten-lebbing.nl>
Signed-off-by: Attila Fülöp <attila@fueloep.org>
Closes openzfs#9659

module/icp/algs/modes/gcm.c

@@ -300,11 +300,13 @@ gcm_mode_decrypt_contiguous_blocks(gcm_ctx_t *ctx, char *data, size_t length,
 	if (length > 0) {
 		new_len = ctx->gcm_pt_buf_len + length;
 		new = vmem_alloc(new_len, ctx->gcm_kmflag);
+		if (new == NULL) {
+			vmem_free(ctx->gcm_pt_buf, ctx->gcm_pt_buf_len);
+			ctx->gcm_pt_buf = NULL;
+			return (CRYPTO_HOST_MEMORY);
+		}
 		bcopy(ctx->gcm_pt_buf, new, ctx->gcm_pt_buf_len);
 		vmem_free(ctx->gcm_pt_buf, ctx->gcm_pt_buf_len);
-		if (new == NULL)
-			return (CRYPTO_HOST_MEMORY);
-
 		ctx->gcm_pt_buf = new;
 		ctx->gcm_pt_buf_len = new_len;
 		bcopy(data, &ctx->gcm_pt_buf[ctx->gcm_processed_data_len],

module/icp/core/kcf_prov_lib.c

@@ -207,9 +207,12 @@ crypto_update_uio(void *ctx, crypto_data_t *input, crypto_data_t *output,
 		cur_len = MIN(uiop->uio_iov[vec_idx].iov_len -
 		    offset, length);
 
-		(cipher)(ctx, uiop->uio_iov[vec_idx].iov_base + offset,
+		int rv = (cipher)(ctx, uiop->uio_iov[vec_idx].iov_base + offset,
 		    cur_len, (input == output) ? NULL : output);
 
+		if (rv != CRYPTO_SUCCESS) {
+			return (rv);
+		}
 		length -= cur_len;
 		vec_idx++;
 		offset = 0;