From: Dan Carpenter <dan.carpenter@oracle.com>
To: Eric Biggers <ebiggers@kernel.org>
Cc: syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org,
"David S . Miller" <davem@davemloft.net>,
Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
netdev@vger.kernel.org, Jakub Kicinski <kuba@kernel.org>,
linux-kernel-mentees@lists.linuxfoundation.org,
Peilin Ye <yepeilin.cs@gmail.com>,
Navid Emamdoost <navid.emamdoost@gmail.com>
Subject: Re: [Linux-kernel-mentees] [PATCH net] qrtr: Fix ZERO_SIZE_PTR deref in qrtr_tun_write_iter()
Date: Mon, 13 Jul 2020 12:13:29 +0300 [thread overview]
Message-ID: <20200713091329.GP2571@kadam> (raw)
In-Reply-To: <20200712213631.GA809@sol.localdomain>
On Sun, Jul 12, 2020 at 02:36:31PM -0700, Eric Biggers wrote:
> On Sun, Jul 12, 2020 at 05:03:00PM -0400, Peilin Ye wrote:
> > qrtr_tun_write_iter() is dereferencing `ZERO_SIZE_PTR`s when `from->count`
> > equals to zero. Fix it by rejecting zero-length kzalloc() requests.
> >
> > This patch fixes the following syzbot bug:
> >
> > https://syzkaller.appspot.com/bug?id=f56bbe6668873ee245986bbd23312b895fa5a50a
> >
> > Reported-by: syzbot+03e343dbccf82a5242a2@syzkaller.appspotmail.com
> > Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> > ---
> > net/qrtr/tun.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/net/qrtr/tun.c b/net/qrtr/tun.c
> > index 15ce9b642b25..5465e94ba8e5 100644
> > --- a/net/qrtr/tun.c
> > +++ b/net/qrtr/tun.c
> > @@ -80,6 +80,9 @@ static ssize_t qrtr_tun_write_iter(struct kiocb *iocb, struct iov_iter *from)
> > ssize_t ret;
> > void *kbuf;
> >
> > + if (!len)
> > + return -EINVAL;
> > +
> > kbuf = kzalloc(len, GFP_KERNEL);
> > if (!kbuf)
> > return -ENOMEM;
>
> Wasn't this already fixed by:
>
> commit 8ff41cc21714704ef0158a546c3c4d07fae2c952
> Author: Dan Carpenter <dan.carpenter@oracle.com>
> Date: Tue Jun 30 14:46:15 2020 +0300
>
> net: qrtr: Fix an out of bounds read qrtr_endpoint_post()
Yep. If you're using kmalloc() you can allocate a zero byte buffer but
you just can't access the array. for (i = 0; i < 0; i++) works.
It's interesting because at the time, I wrote the patch I thought "len"
probably couldn't be zero but I just checked it for completeness and
readability.
regards,
dan carpenter
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prev parent reply other threads:[~2020-07-13 9:13 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-12 21:03 [Linux-kernel-mentees] [PATCH net] qrtr: Fix ZERO_SIZE_PTR deref in qrtr_tun_write_iter() Peilin Ye
2020-07-12 21:36 ` Eric Biggers
2020-07-13 9:13 ` Dan Carpenter [this message]
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