linux-kernel - Re: [Linux-kernel-mentees] [PATCH net] AX.25: Fix out-of-bounds read in ax25

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Message-ID: <20200723151548.GB412829@PWN>
Date:   Thu, 23 Jul 2020 11:15:48 -0400
From:   Peilin Ye <yepeilin.cs@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     jreuter@...na.de, ralf@...ux-mips.org, gregkh@...uxfoundation.org,
        syzkaller-bugs@...glegroups.com,
        linux-kernel-mentees@...ts.linuxfoundation.org, kuba@...nel.org,
        linux-hams@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [Linux-kernel-mentees] [PATCH net] AX.25: Fix out-of-bounds read
 in ax25_connect()

On Wed, Jul 22, 2020 at 05:57:14PM -0700, David Miller wrote:
> From: Peilin Ye <yepeilin.cs@...il.com>
> Date: Wed, 22 Jul 2020 11:19:01 -0400
> 
> > 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@...kaller.appspotmail.com
> > Link: https://syzkaller.appspot.com/bug?id=55ef9d629f3b3d7d70b69558015b63b48d01af66
> > Signed-off-by: Peilin Ye <yepeilin.cs@...il.com>
> 
> Applied and queued up for -stable, thanks.

Thank you for reviewing my patch!

Peilin Ye