Commit 2f2a7ffa authored Jul 22, 2020 by Peilin Ye Committed by David S. Miller Jul 22, 2020

AX.25: Fix out-of-bounds read in ax25_connect()



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 <yepeilin.cs@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 26cb7085

net/ax25/af_ax25.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}

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