From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELv/p62ZEH1AQojmW7KpzqrKDzhaOUPFwvPSoFr+2F7UKiqGv1MpJVd3aqwmZx2lmlSxScOK ARC-Seal: i=1; a=rsa-sha256; t=1519411826; cv=none; d=google.com; s=arc-20160816; b=D86gd2LXcVZ44acKXIKpVeNMpYaqS9zJ8zGFE3wSliA7pKNRXRdrw4TQ3TqhrDlX0w UuYFNy0QnNjPRbBwCSlpMFK+kx21GoTC6fs51CHbT+o2aACWq3bHufGOpgj7Zvf7RJpo 15RBzefGxFunlqLlS8rlnCasyXkwR4YO8pWbCn2dPdUMQK3lZzNgPYHNWgndwYm4RB5C JJTJwvJ+7vsGUDy6IwPpONi3K3Xvv4OaFnJy4d240xEj2+CgehtUuERIVAnYDtT1duuw kSTRznWbRWDH+Skgzund6PABFFVr2SyjZsB2K7g9OyeC5LmNbe7gPcRd0/7LED0ToZjw 7gPg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=c1mtNUK2cfuldYUwjqEFOSqmLNB6wiNROOupBYxXYgg=; b=u6TzgcO70Uj6pWAFwqJptHYuVENMmXFxqf8hNv8FMXdZpqwbzAKAcEdI6/qsOvTFrP mRbRfMy8QysaGF9/QIJ7njaRsYcIHtRoTWF1BCNLJfH98T90gdnJLPkdy5EAB+NLb9Ax pveN8uQhLHsbHprGbPlbWzTSNEx9F/Gx4CzRaa3UhlbAnOHeJ4F//zd7SzmfqFL/5GWN ibR42Qe0yLugjOnD8Vd/CUzudDfmiQFb0RQxtmmBM1f7QYeex2R11/uup/SauX+ehj3I uz8tIm901kp9/8IwWPyO6BSuRlgYcPkjgb41QxHOdf8IGyiDPGXtV1Eo7WXbwMCPeFXz d3JA== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+114b15f2be420a8886c3@syzkaller.appspotmail.com, Tom Herbert , Eric Dumazet , "David S. Miller" Subject: [PATCH 4.14 003/159] kcm: Check if sk_user_data already set in kcm_attach Date: Fri, 23 Feb 2018 19:25:11 +0100 Message-Id: <20180223170743.496615531@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180223170743.086611315@linuxfoundation.org> References: <20180223170743.086611315@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1593218387524448381?= X-GMAIL-MSGID: =?utf-8?q?1593218775770517556?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tom Herbert commit e5571240236c5652f3e079b1d5866716a7ad819c upstream. This is needed to prevent sk_user_data being overwritten. The check is done under the callback lock. This should prevent a socket from being attached twice to a KCM mux. It also prevents a socket from being attached for other use cases of sk_user_data as long as the other cases set sk_user_data under the lock. Followup work is needed to unify all the use cases of sk_user_data to use the same locking. Reported-by: syzbot+114b15f2be420a8886c3@syzkaller.appspotmail.com Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module") Signed-off-by: Tom Herbert Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/kcm/kcmsock.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c @@ -1405,9 +1405,18 @@ static int kcm_attach(struct socket *soc return err; } - sock_hold(csk); - write_lock_bh(&csk->sk_callback_lock); + + /* Check if sk_user_data is aready by KCM or someone else. + * Must be done under lock to prevent race conditions. + */ + if (csk->sk_user_data) { + write_unlock_bh(&csk->sk_callback_lock); + strp_done(&psock->strp); + kmem_cache_free(kcm_psockp, psock); + return -EALREADY; + } + psock->save_data_ready = csk->sk_data_ready; psock->save_write_space = csk->sk_write_space; psock->save_state_change = csk->sk_state_change; @@ -1415,8 +1424,11 @@ static int kcm_attach(struct socket *soc csk->sk_data_ready = psock_data_ready; csk->sk_write_space = psock_write_space; csk->sk_state_change = psock_state_change; + write_unlock_bh(&csk->sk_callback_lock); + sock_hold(csk); + /* Finished initialization, now add the psock to the MUX. */ spin_lock_bh(&mux->lock); head = &mux->psocks;