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Date:   Wed, 17 Jun 2020 21:15:26 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Fedor Tokarev <ftokarev@...il.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>,
        Sasha Levin <sashal@...nel.org>, linux-nfs@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 201/266] net: sunrpc: Fix off-by-one issues in 'rpc_ntop6'

From: Fedor Tokarev <ftokarev@...il.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@...il.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Sasha Levin <sashal@...nel.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 d024af4be85e..105d17af4abc 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);
-- 
2.25.1

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