lib: os: cbprintf: Add alignment check to cbprintf_package

Added validation of alignment to cbprintf_package. Error is returned if
input buffer is not aligned to the largest argument.

Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>

include/sys/cbprintf.h

@@ -139,6 +139,7 @@ typedef int (*cbprintf_cb)(/* int c, void *ctx */);
  * @retval nonegative the number of bytes successfully stored at @p packaged.
  * This will not exceed @p len.
  * @retval -EINVAL if @p format is not acceptable
+ * @retval -EFAULT if @p packaged alignment is not acceptable
  * @retval -ENOSPC if @p packaged was not null and the space required to store
  * exceed @p len.
  */

lib/os/cbprintf_packaged.c

@@ -374,6 +374,11 @@ int cbvprintf_package(void *packaged, size_t len,
 		/* align destination buffer location */
 		buf = (void *) ROUND_UP(buf, align);
 
+		/* Check if buffer is properly aligned. */
+		if ((uintptr_t)buf0 & (align - 1)) {
+			return -EFAULT;
+		}
+
 		/* make sure the data fits */
 		if (buf0 && buf - buf0 + size > len) {
 			return -ENOSPC;