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

Message ID 20200328115650.GA27729@laptop (mailing list archive)
State New, archived
Headers show
Series net: sunrpc: Fix off-by-one issues in 'rpc_ntop6' | expand

Commit Message

Fedor Tokarev March 28, 2020, 11:56 a.m. UTC
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>
 net/sunrpc/addr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
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diff --git a/net/sunrpc/addr.c b/net/sunrpc/addr.c
index 8b4d72b..010dcb8 100644
--- 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);