crypto: iaa - Fix out-of-bounds index in find_empty_iaa_compression_mode

commit 4832930 upstream.

The local variable 'i' is initialized with -EINVAL, but the for loop
immediately overwrites it and -EINVAL is never returned.

If no empty compression mode can be found, the function would return the
out-of-bounds index IAA_COMP_MODES_MAX, which would cause an invalid
array access in add_iaa_compression_mode().

Fix both issues by returning either a valid index or -EINVAL.

Cc: stable@vger.kernel.org
Fixes: b190447 ("crypto: iaa - Add compression mode management along with fixed mode")
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Acked-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: toblux

drivers/crypto/intel/iaa/iaa_crypto_main.c

@@ -223,15 +223,13 @@ static struct iaa_compression_mode *iaa_compression_modes[IAA_COMP_MODES_MAX];
 
 static int find_empty_iaa_compression_mode(void)
 {
-	int i = -EINVAL;
+	int i;
 
-	for (i = 0; i < IAA_COMP_MODES_MAX; i++) {
-		if (iaa_compression_modes[i])
-			continue;
-		break;
-	}
+	for (i = 0; i < IAA_COMP_MODES_MAX; i++)
+		if (!iaa_compression_modes[i])
+			return i;
 
-	return i;
+	return -EINVAL;
 }
 
 static struct iaa_compression_mode *find_iaa_compression_mode(const char *name, int *idx)