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

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>
This commit is contained in:
Fedor Tokarev 2020-03-28 14:56:55 +03:00 committed by Anna Schumaker
parent 00a7a00e2d
commit 118917d696

View File

@ -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);