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+c82752228ed975b0a...@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=55ef9d629f3b3d7d70b69558015b63b48d01af66 Signed-off-by: Peilin Ye <yepeilin...@gmail.com> --- 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; } -- 2.25.1
