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

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Message-Id: <20200722.175714.1713497446730685740.davem@davemloft.net>
Date:   Wed, 22 Jul 2020 17:57:14 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     yepeilin.cs@...il.com
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()

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.