math: fft: fix error path in mod_fft_multi_plan_new()

The error path of mod_fft_multi_plan_new() had two related bugs. With
num_ffts == 1 the temporary input buffer aliases the caller-provided
inb, but the err_free_buffer label freed plan->tmp_i32[0]
unconditionally, which would have released the caller's buffer. With
num_ffts == 3, a failure in the second or third fft_plan_common_new()
call only freed the shared scratch buffer and the bit-reverse table,
leaking the previously allocated fft_plan entries.

Collapse all error labels into a single err: that calls
mod_fft_multi_plan_free(). That helper already walks fft_plan[] (NULL
slots from the initial mod_zalloc() are no-ops in mod_free()) and only
frees tmp_i32[0] when num_ffts > 1, so both issues are handled in one
place.

Signed-off-by: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>

Author: singalsu

src/math/fft/fft_multi.c

@@ -75,7 +75,7 @@ struct fft_multi_plan *mod_fft_multi_plan_new(struct processing_module *mod, voi
 			plan->tmp_i32[0] = mod_balloc(mod, tmp_size);
 			if (!plan->tmp_i32[0]) {
 				comp_cl_err(mod->dev, "Failed to allocate FFT buffers");
-				goto err_free_bit_reverse;
+				goto err;
 			}
 
 			/* Set up buffers */
@@ -95,7 +95,7 @@ struct fft_multi_plan *mod_fft_multi_plan_new(struct processing_module *mod, voi
 								plan->tmp_o32[i],
 								plan->fft_size, 32);
 			if (!plan->fft_plan[i])
-				goto err_free_buffer;
+				goto err;
 
 			plan->fft_plan[i]->bit_reverse_idx = plan->bit_reverse_idx;
 		}
@@ -110,14 +110,13 @@ struct fft_multi_plan *mod_fft_multi_plan_new(struct processing_module *mod, voi
 				  plan->fft_plan[0]->len);
 	return plan;
 
-err_free_buffer:
-	mod_free(mod, plan->tmp_i32[0]);
-
-err_free_bit_reverse:
-	mod_free(mod, plan->bit_reverse_idx);
-
 err:
-	mod_free(mod, plan);
+	/* mod_fft_multi_plan_free() handles partial state safely:
+	 *  - fft_plan[i] entries left NULL by mod_zalloc are skipped by mod_free,
+	 *  - tmp_i32[0] is freed only when num_ffts > 1, so it does not free
+	 *    the caller-provided inb in the single-FFT case.
+	 */
+	mod_fft_multi_plan_free(mod, plan);
 	return NULL;
 }