On Thu, Jul 23, 2020 at 06:50:58PM +0300, Dan Carpenter wrote: > On Thu, Jul 23, 2020 at 11:13:55AM -0400, Peilin Ye wrote: > > On Thu, Jul 23, 2020 at 05:28:15PM +0300, Dan Carpenter wrote: > > > On Wed, Jul 22, 2020 at 11:19:01AM -0400, Peilin Ye wrote: > > > > 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) { > > > > > > The "sizeof(ax25_address) * fsa->fsa_ax25.sax25_ndigis" can have an > > > integer overflow so you still need the > > > "fsa->fsa_ax25.sax25_ndigis > AX25_MAX_DIGIS" check. > > > > Thank you for fixing this up! I did some math but I didn't think of > > that. Will be more careful when removing things. > > No problem. You had the right approach to look for ways to clean things > up. > > Your patches make me happy because you're trying to fix important bugs.
It is very encouraging to hear that! I will try to do what I can do. Thank you, Peilin Ye
