net: sunrpc: Fix off-by-one issues in 'rpc_ntop6'

[ Upstream commit 118917d696dc59fd3e1741012c2f9db2294bed6f ]

Fix off-by-one issues in 'rpc_ntop6':
 - 'snprintf' returns the number of characters which would have been
   written if enough space had been available, excluding the terminating
   null byte. Thus, a return value of 'sizeof(scopebuf)' means that the
   last character was dropped.
 - 'strcat' adds a terminating null byte to the string, thus if len ==
   buflen, the null byte is written past the end of the buffer.

Signed-off-by: Fedor Tokarev <ftokarev@gmail.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/sunrpc/addr.c b/net/sunrpc/addr.c
index d024af4..105d17a 100644 (file)
--- a/net/sunrpc/addr.c
+++ b/net/sunrpc/addr.c
@@ -82,11 +82,11 @@ static size_t rpc_ntop6(const struct sockaddr *sap,
 
        rc = snprintf(scopebuf, sizeof(scopebuf), "%c%u",
                        IPV6_SCOPE_DELIMITER, sin6->sin6_scope_id);
-       if (unlikely((size_t)rc > sizeof(scopebuf)))
+       if (unlikely((size_t)rc >= sizeof(scopebuf)))
                return 0;
 
        len += rc;
-       if (unlikely(len > buflen))
+       if (unlikely(len >= buflen))
                return 0;
 
        strcat(buf, scopebuf);