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[76.119.149.155]) by smtp.gmail.com with ESMTPSA id 16sm147427qkv.48.2020.07.22.08.20.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Jul 2020 08:20:16 -0700 (PDT) From: Peilin Ye To: Joerg Reuter , Ralf Baechle Cc: Peilin Ye , Greg Kroah-Hartman , syzkaller-bugs@googlegroups.com, linux-kernel-mentees@lists.linuxfoundation.org, "David S . Miller" , Jakub Kicinski , linux-hams@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [Linux-kernel-mentees] [PATCH net] AX.25: Fix out-of-bounds read in ax25_connect() Date: Wed, 22 Jul 2020 11:19:01 -0400 Message-Id: <20200722151901.350003-1-yepeilin.cs@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Checks on `addr_len` and `fsa->fsa_ax25.sax25_ndigis` are insufficient. ax25_connect() can go out of bounds when `fsa->fsa_ax25.sax25_ndigis` equals to 7 or 8. Fix it. This issue has been reported as a KMSAN uninit-value bug, because in such a case, ax25_connect() reaches into the uninitialized portion of the `struct sockaddr_storage` statically allocated in __sys_connect(). It is safe to remove `fsa->fsa_ax25.sax25_ndigis > AX25_MAX_DIGIS` because `addr_len` is guaranteed to be less than or equal to `sizeof(struct full_sockaddr_ax25)`. Reported-by: syzbot+c82752228ed975b0a623@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=55ef9d629f3b3d7d70b69558015b63b48d01af66 Signed-off-by: Peilin Ye --- net/ax25/af_ax25.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index fd91cd34f25e..ef5bf116157a 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -1187,7 +1187,9 @@ static int __must_check ax25_connect(struct socket *sock, if (addr_len > sizeof(struct sockaddr_ax25) && fsa->fsa_ax25.sax25_ndigis != 0) { /* Valid number of digipeaters ? */ - if (fsa->fsa_ax25.sax25_ndigis < 1 || fsa->fsa_ax25.sax25_ndigis > AX25_MAX_DIGIS) { + if (fsa->fsa_ax25.sax25_ndigis < 1 || + addr_len < sizeof(struct sockaddr_ax25) + + sizeof(ax25_address) * fsa->fsa_ax25.sax25_ndigis) { err = -EINVAL; goto out_release; }