Avoid undefined behavior with high interface index

Cherry-pick from aosp/2125173

Behavior of bitwise left shift is undefined when the right operator is
greater than the number of bits in the left operand; so the code relied
on undefined behavior when interface indexes were >= 32.

Just use a boolean instead, as the result was only used as a boolean.

Also do not limit reads in if_inet6 to 1 byte for address flags, scope
value, and prefix length, as there is no good reason to do so, and this
is in line with more recent upstream versions and the interface index
read. In practice prefix length, scope value and interface flags should
not be above 255 so this should be a no-op.

Bug: 235797641
Test: atest NsdManagerTest --rerun-until-failure 50
Change-Id: I41fae1900400779cecb715e8cfb1e662b88fd41d
Merged-In: I41fae1900400779cecb715e8cfb1e662b88fd41d

2 files changed, 10 insertions, 14 deletions

diff --git a/mDNSPosix/mDNSPosix.c b/mDNSPosix/mDNSPosix.c
index 8960c93..28f4e06 100644
--- a/mDNSPosix/mDNSPosix.c
+++ b/mDNSPosix/mDNSPosix.c
@@ -1102,14 +1102,14 @@ mDNSlocal void		PrintNetLinkMsg(const struct nlmsghdr *pNLMsg)
 	}
 #endif
 
-mDNSlocal mDNSu32		ProcessRoutingNotification(int sd)
+mDNSlocal mDNSBool		ProcessRoutingNotification(int sd)
 // Read through the messages on sd and if any indicate that any interface records should
 // be torn down and rebuilt, return affected indices as a bitmask. Otherwise return 0.
 	{
 	ssize_t					readCount;
 	char					buff[4096];	
 	struct nlmsghdr			*pNLMsg = (struct nlmsghdr*) buff;
-	mDNSu32				result = 0;
+	mDNSBool				result = mDNSfalse;
 	
 	// The structure here is more complex than it really ought to be because,
 	// unfortunately, there's no good way to size a buffer in advance large
@@ -1144,10 +1144,9 @@ mDNSlocal mDNSu32		ProcessRoutingNotification(int sd)
 #endif
 
 		// Process the NetLink message
-		if (pNLMsg->nlmsg_type == RTM_GETLINK || pNLMsg->nlmsg_type == RTM_NEWLINK)
-			result |= 1 << ((struct ifinfomsg*) NLMSG_DATA(pNLMsg))->ifi_index;
-		else if (pNLMsg->nlmsg_type == RTM_DELADDR || pNLMsg->nlmsg_type == RTM_NEWADDR)
-			result |= 1 << ((struct ifaddrmsg*) NLMSG_DATA(pNLMsg))->ifa_index;
+		if (pNLMsg->nlmsg_type == RTM_GETLINK || pNLMsg->nlmsg_type == RTM_NEWLINK ||
+				pNLMsg->nlmsg_type == RTM_DELADDR || pNLMsg->nlmsg_type == RTM_NEWADDR)
+			result = mDNStrue;
 
 		// Advance pNLMsg to the next message in the buffer
 		if ((pNLMsg->nlmsg_flags & NLM_F_MULTI) != 0 && pNLMsg->nlmsg_type != NLMSG_DONE)
@@ -1191,14 +1190,14 @@ mDNSlocal void		PrintRoutingSocketMsg(const struct ifa_msghdr *pRSMsg)
 	}
 #endif
 
-mDNSlocal mDNSu32		ProcessRoutingNotification(int sd)
+mDNSlocal mDNSBool		ProcessRoutingNotification(int sd)
 // Read through the messages on sd and if any indicate that any interface records should
 // be torn down and rebuilt, return affected indices as a bitmask. Otherwise return 0.
 	{
 	ssize_t					readCount;
 	char					buff[4096];	
 	struct ifa_msghdr		*pRSMsg = (struct ifa_msghdr*) buff;
-	mDNSu32				result = 0;
+	mDNSBool				result = mDNSfalse;
 
 	readCount = read(sd, buff, sizeof buff);
 	if (readCount < (ssize_t) sizeof(struct ifa_msghdr))
@@ -1212,10 +1211,7 @@ mDNSlocal mDNSu32		ProcessRoutingNotification(int sd)
 	if (pRSMsg->ifam_type == RTM_NEWADDR || pRSMsg->ifam_type == RTM_DELADDR ||
 		 pRSMsg->ifam_type == RTM_IFINFO)
 		{
-		if (pRSMsg->ifam_type == RTM_IFINFO)
-			result |= 1 << ((struct if_msghdr*) pRSMsg)->ifm_index;
-		else
-			result |= 1 << pRSMsg->ifam_index;
+		result = mDNStrue;
 		}
 
 	return result;
@@ -1228,7 +1224,7 @@ mDNSlocal void InterfaceChangeCallback(int fd, short filter, void *context)
 	{
 	IfChangeRec		*pChgRec = (IfChangeRec*) context;
 	fd_set			readFDs;
-	mDNSu32		changedInterfaces = 0;
+	mDNSBool		changedInterfaces = mDNSfalse;
 	struct timeval	zeroTimeout = { 0, 0 };
 
 	(void)fd; // Unused
diff --git a/mDNSPosix/mDNSUNP.c b/mDNSPosix/mDNSUNP.c
index f5d0c52..0e3632b 100755
--- a/mDNSPosix/mDNSUNP.c
+++ b/mDNSPosix/mDNSUNP.c
@@ -106,7 +106,7 @@ struct ifi_info *get_ifi_info_linuxv6(int family, int doaliases)
 			goto gotError;
 		}
 		while (fscanf(fp,
-					  "%4s%4s%4s%4s%4s%4s%4s%4s %x %02x %02x %02x %15s\n",
+					  "%4s%4s%4s%4s%4s%4s%4s%4s %x %x %x %x %15s\n",
 					  addr[0],addr[1],addr[2],addr[3],
 					  addr[4],addr[5],addr[6],addr[7],
 					  &index, &plen, &scope, &flags, ifname) != EOF) {