rework login and discovery code to avoid strlen beyond end of data

Message-id: <1383729402-27559-11-git-send-email-pbonzini@redhat.com>
Patchwork-id: 55505
O-Subject: [PATCH 10/11] rework login and discovery code to avoid strlen beyond end of data
Bugzilla: 1026820
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Acked-by: Orit Wasserman <owasserm@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

Checking for the presence of the NUL character should be done
without accessing beyond the PDU datain.  Use memchr instead
of strlen, and compute the length only if a NUL character is
actually there.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit bfde49756524bd3748234dc6dfa8015e37176e9b)

Conflicts:
	lib/login.c
---
 lib/discovery.c | 31 ++++++++++++++++++++-----------
 lib/login.c     | 32 +++++++++++++++++++++-----------
 2 files changed, 41 insertions(+), 22 deletions(-)
diff --git a/lib/discovery.c b/lib/discovery.c
index 1ddf8ef..7396e71 100644
--- a/lib/discovery.c
+++ b/lib/discovery.c
@@ -112,25 +112,34 @@ iscsi_process_text_reply(struct iscsi_context *iscsi, struct iscsi_pdu *pdu,
 			      pdu->private_data);
 		return -1;
 	}
+	if (size == 0) {
+		iscsi_set_error(iscsi, "size == 0 when parsing "
+				"discovery data");
+		pdu->callback(iscsi, SCSI_STATUS_ERROR, NULL,
+			      pdu->private_data);
+		return -1;
+	}
 
-	while (size > 0) {
+	do {
+		unsigned char *end;
 		int len;
 
-		len = strlen((char *)ptr);
-
-		if (len == 0) {
-			break;
-		}
-
-		if (len > size) {
-			iscsi_set_error(iscsi, "len > size when parsing "
-					"discovery data %d>%d", len, size);
+		end = memchr(ptr, 0, size);
+		if (end == NULL) {
+			iscsi_set_error(iscsi, "NUL not found after offset %td "
+					"when parsing discovery data",
+					ptr - in->data);
 			pdu->callback(iscsi, SCSI_STATUS_ERROR, NULL,
 				      pdu->private_data);
 			iscsi_free_discovery_addresses(iscsi, targets);
 			return -1;
 		}
 
+		len = end - ptr;
+		if (len == 0) {
+			break;
+		}
+
 		/* parse the strings */
 		if (!strncmp((char *)ptr, "TargetName=", 11)) {
 			struct iscsi_discovery_address *target;
@@ -181,7 +190,7 @@ iscsi_process_text_reply(struct iscsi_context *iscsi, struct iscsi_pdu *pdu,
 
 		ptr  += len + 1;
 		size -= len + 1;
-	}
+	} while (size > 0);
 
 	pdu->callback(iscsi, SCSI_STATUS_GOOD, targets, pdu->private_data);
 	iscsi_free_discovery_addresses(iscsi, targets);
diff --git a/lib/login.c b/lib/login.c
index 22a7408..8b696b0 100644
--- a/lib/login.c
+++ b/lib/login.c
@@ -1000,29 +1000,39 @@ iscsi_process_login_reply(struct iscsi_context *iscsi, struct iscsi_pdu *pdu,
 		iscsi->maxcmdsn = maxcmdsn;
 	}
 	
+	if (size == 0) {
+	       iscsi_set_error(iscsi, "size == 0 when parsing "
+			       "login data");
+	       pdu->callback(iscsi, SCSI_STATUS_ERROR, NULL,
+			     pdu->private_data);
+	       return -1;
+	}
+
 	/* XXX here we should parse the data returned in case the target
 	 * renegotiated some some parameters.
 	 *  we should also do proper handshaking if the target is not yet
 	 * prepared to transition to the next stage
 	 */
 
-	while (size > 0) {
+	do {
+		char *end;
 		int len;
 
-		len = strlen(ptr);
-
-		if (len == 0) {
-			break;
-		}
-
-		if (len > size) {
-			iscsi_set_error(iscsi, "len > size when parsing "
-					"login data %d>%d", len, size);
+		end = memchr(ptr, 0, size);
+		if (end == NULL) {
+			iscsi_set_error(iscsi, "NUL not found after offset %td "
+					"when parsing login data",
+					(unsigned char *)ptr - in->data);
 			pdu->callback(iscsi, SCSI_STATUS_ERROR, NULL,
 				      pdu->private_data);
 			return -1;
 		}
 
+		len = end - ptr;
+		if (len == 0) {
+			break;
+		}
+
 		/* parse the strings */
 		if (!strncmp(ptr, "TargetAddress=", 14)) {
 			strncpy(iscsi->target_address,ptr+14,MAX_STRING_SIZE);
@@ -1095,7 +1105,7 @@ iscsi_process_login_reply(struct iscsi_context *iscsi, struct iscsi_pdu *pdu,
 
 		ptr  += len + 1;
 		size -= len + 1;
-	}
+	} while (size > 0);
 
 	if (status == SCSI_STATUS_REDIRECT && iscsi->target_address[0]) {
 		ISCSI_LOG(iscsi, 2, "target requests redirect to %s",iscsi->target_address);