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 808309446 for ; Sun, 13 Aug 2023 21:47:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0387FC433C8; Sun, 13 Aug 2023 21:47:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1691963260; bh=FMei2CsV7GQhJ+i9pA7bSCfp/3BI5AitEfoTp59/bpM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CKc5ME0KUJiqLK3hd/GJg/hWpcyeGaFY1RxjdMdF1k2YCEjx9i0AHlIaMCoFcyoBc t1PfElWdtgsNNN+bj5jDCnm67/jrZok0Yn71TSLAif+FNUos6srkr4BzlXWEDeMi7o D00WDGHcX3niZ17cI6pfmNkP94eQKi/DClsQT6bA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot , Eric Dumazet , Jakub Kicinski Subject: [PATCH 5.4 21/39] dccp: fix data-race around dp->dccps_mss_cache Date: Sun, 13 Aug 2023 23:20:12 +0200 Message-ID: <20230813211705.551589989@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230813211704.796906808@linuxfoundation.org> References: <20230813211704.796906808@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 @@ -185,7 +185,7 @@ 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 @@ -644,7 +644,7 @@ 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); @@ -766,7 +766,7 @@ int dccp_sendmsg(struct sock *sk, struct trace_dccp_probe(sk, len); - if (len > dp->dccps_mss_cache) + if (len > READ_ONCE(dp->dccps_mss_cache)) return -EMSGSIZE; lock_sock(sk); @@ -799,6 +799,12 @@ 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)