[PATCH AUTOSEL 4.9 66/80] net: sunrpc: Fix off-by-one issues in 'rpc_ntop6'

Sasha Levin
2020-06-18T01:41:26Z

From: Fedor Tokarev <ftokarev@gmail.com>

[ 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>
---
net/sunrpc/addr.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sunrpc/addr.c b/net/sunrpc/addr.c
index 2e0a6f92e563..8391c2785550 100644
--- a/net/sunrpc/addr.c
+++ b/net/sunrpc/addr.c
@@ -81,11 +81,11 @@ 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);
--
2.25.1