linux-kernel - [PATCH] net: sunrpc: Fix off-by-one issues in 'rpc

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Message-ID: <20200328115650.GA27729@laptop>
Date:   Sat, 28 Mar 2020 14:56:55 +0300
From:   Fedor Tokarev <ftokarev@...il.com>
To:     bfields@...ldses.org, chuck.lever@...cle.com,
        anna.schumaker@...app.com, trond.myklebust@...merspace.com,
        davem@...emloft.net, kuba@...nel.org
Cc:     linux-nfs@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] 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@...il.com>
---
 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 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);
-- 
2.7.4