From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7AD9B9443 for ; Sun, 13 Aug 2023 21:21:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED21AC433C7; Sun, 13 Aug 2023 21:21:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1691961666; bh=c+2LWefcHW//g9WMKgWlvMWqrW8stZ7s7bhip9HllYE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZsPxoRRNmSJla8BWgzQWKhRXubauimuMy4nNloULXgSsb3knK96wc70WwkKm0EBeb 14zYxtE8obIC3miMTF4SFwKFKakD73SohG7lKZaXa0XdDLftNtM3PYm94N4kv50/7s 6ZjoB6cupbgFzbugqRjG1uAUDwFGK3mCyQlgjq88= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot , Eric Dumazet , Jakub Kicinski Subject: [PATCH 4.14 16/26] dccp: fix data-race around dp->dccps_mss_cache Date: Sun, 13 Aug 2023 23:19:09 +0200 Message-ID: <20230813211703.597664050@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230813211702.980427106@linuxfoundation.org> References: <20230813211702.980427106@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Eric Dumazet commit a47e598fbd8617967e49d85c49c22f9fc642704c upstream. dccp_sendmsg() reads dp->dccps_mss_cache before locking the socket. Same thing in do_dccp_getsockopt(). Add READ_ONCE()/WRITE_ONCE() annotations, and change dccp_sendmsg() to check again dccps_mss_cache after socket is locked. Fixes: 7c657876b63c ("[DCCP]: Initial implementation") Reported-by: syzbot Signed-off-by: Eric Dumazet Link: https://lore.kernel.org/r/20230803163021.2958262-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/dccp/output.c | 2 +- net/dccp/proto.c | 10 ++++++++-- 2 files changed, 9 insertions(+), 3 deletions(-) --- a/net/dccp/output.c +++ b/net/dccp/output.c @@ -189,7 +189,7 @@ unsigned int dccp_sync_mss(struct sock * /* And store cached results */ icsk->icsk_pmtu_cookie = pmtu; - dp->dccps_mss_cache = cur_mps; + WRITE_ONCE(dp->dccps_mss_cache, cur_mps); return cur_mps; } --- a/net/dccp/proto.c +++ b/net/dccp/proto.c @@ -645,7 +645,7 @@ static int do_dccp_getsockopt(struct soc return dccp_getsockopt_service(sk, len, (__be32 __user *)optval, optlen); case DCCP_SOCKOPT_GET_CUR_MPS: - val = dp->dccps_mss_cache; + val = READ_ONCE(dp->dccps_mss_cache); break; case DCCP_SOCKOPT_AVAILABLE_CCIDS: return ccid_getsockopt_builtin_ccids(sk, len, optval, optlen); @@ -765,7 +765,7 @@ int dccp_sendmsg(struct sock *sk, struct int rc, size; long timeo; - if (len > dp->dccps_mss_cache) + if (len > READ_ONCE(dp->dccps_mss_cache)) return -EMSGSIZE; lock_sock(sk); @@ -798,6 +798,12 @@ int dccp_sendmsg(struct sock *sk, struct goto out_discard; } + /* We need to check dccps_mss_cache after socket is locked. */ + if (len > dp->dccps_mss_cache) { + rc = -EMSGSIZE; + goto out_discard; + } + skb_reserve(skb, sk->sk_prot->max_header); rc = memcpy_from_msg(skb_put(skb, len), msg, len); if (rc != 0)