tipc: avoid possible string overflow

gcc points out that the combined length of the fixed-length inputs to
l->name is larger than the destination buffer size:

net/tipc/link.c: In function 'tipc_link_create':
net/tipc/link.c:465:26: error: '%s' directive writing up to 32 bytes
into a region of size between 26 and 58 [-Werror=format-overflow=]
sprintf(l->name, "%s:%s-%s:unknown", self_str, if_name, peer_str);

net/tipc/link.c:465:2: note: 'sprintf' output 11 or more bytes
(assuming 75) into a destination of size 60
sprintf(l->name, "%s:%s-%s:unknown", self_str, if_name, peer_str);

A detailed analysis reveals that the theoretical maximum length of
a link name is:
max self_str + 1 + max if_name + 1 + max peer_str + 1 + max if_name =
16 + 1 + 15 + 1 + 16 + 1 + 15 = 65
Since we also need space for a trailing zero we now set MAX_LINK_NAME
to 68.

Just to be on the safe side we also replace the sprintf() call with
snprintf().

Fixes: 25b0b9c4e835 ("tipc: handle collisions of 32-bit node address
hash values")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/tipc.h b/include/uapi/linux/tipc.h
index 156224ac3d745f75eabda995791ab97354e4405b..bf6d28677cfe01d6b482591b5428474acf3d0d9a 100644 (file)
--- a/include/uapi/linux/tipc.h
+++ b/include/uapi/linux/tipc.h
@@ -216,7 +216,7 @@ struct tipc_group_req {
 #define TIPC_MAX_MEDIA_NAME    16
 #define TIPC_MAX_IF_NAME       16
 #define TIPC_MAX_BEARER_NAME   32
-#define TIPC_MAX_LINK_NAME     60
+#define TIPC_MAX_LINK_NAME     68
 
 #define SIOCGETLINKNAME                SIOCPROTOPRIVATE
 

diff --git a/net/tipc/link.c b/net/tipc/link.c
index 8f2a9496439b6c117eec57d276aa03d055511afb..695acb783969730e448579772dfa3a17b3e827d6 100644 (file)
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -462,7 +462,8 @@ bool tipc_link_create(struct net *net, char *if_name, int bearer_id,
                        sprintf(peer_str, "%x", peer);
        }
        /* Peer i/f name will be completed by reset/activate message */
-       sprintf(l->name, "%s:%s-%s:unknown", self_str, if_name, peer_str);
+       snprintf(l->name, sizeof(l->name), "%s:%s-%s:unknown",
+                self_str, if_name, peer_str);
 
        strcpy(l->if_name, if_name);
        l->addr = peer;