[PATCH 2/5] discover/platform-powerpc: limit mailbox response size

[Maxim Polyakov]

The maximum size of the mailbox with Boot Initiator info is defined in
the specification (1). The code should not extract data from the IPMI
response message if its size exceeds the maximum limit from the
specification.

[1] page 398, IPMI Specification v2.0, Revision 1.1, October 1, 2013

Signed-off-by: Maxim Polyakov <m.polyakov at yadro.com>
---
 discover/platform-powerpc.c | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/discover/platform-powerpc.c b/discover/platform-powerpc.c
index 6651e3f..1e33bf1 100644
--- a/discover/platform-powerpc.c
+++ b/discover/platform-powerpc.c
@@ -461,24 +461,27 @@ static int get_ipmi_boot_mailbox_block(struct platform_powerpc *platform,
 		return -1;
 	}
 
-	if (resp_len < sizeof(resp)) {
-		if (resp_len < 4) {
-			pb_log("platform: unexpected length (%d) in "
-					"boot options mailbox response\n",
-					resp_len);
-			return -1;
-		}
+	if (resp_len > sizeof(resp)) {
+		pb_debug("platform: invalid mailbox response size!\n");
+		return -1;
+	}
 
-		if (resp_len == 4) {
-			pb_debug_fn("block %hu empty\n", block);
-			return 0;
-		}
+	if (resp_len < 4) {
+		pb_log("platform: unexpected length (%d) in "
+				"boot options mailbox response\n",
+				resp_len);
+		return -1;
+	}
 
-		blocksize = sizeof(resp) - 4;
-		pb_debug_fn("Mailbox block %hu returns only %zu bytes in block\n",
-				block, blocksize);
+	if (resp_len == 4) {
+		pb_debug_fn("block %hu empty\n", block);
+		return 0;
 	}
 
+	blocksize = sizeof(resp) - 4;
+	pb_debug_fn("Mailbox block %hu returns only %zu bytes in block\n",
+			block, blocksize);
+
 	debug_buf = format_buffer(platform, resp, resp_len);
 	pb_debug_fn("IPMI bootdev mailbox block %hu:\n%s\n", block, debug_buf);
 	talloc_free(debug_buf);
-- 
2.7.4