From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794458682; b=0nMkhXkfubuhNUw2dtHqtHdv+QZeh+kumKS/dANPCXQVlA4c1CdsB2t6+AcA+U+aaXjP vszWW99dYtXAnNoaSn1YU2onim40MgTMgOjetpHrNczec1vZjDiw7OyivHTtTDTr19sX2 C1J/IIbNe7qmkUsbhaFOt19fgsr5iGIOklYd14hpBH65CafnDhOp/N+iN/pwElb1qxyBj 6C2AMwhvt2ivCcoH81s+/vRJ3RuKrvGLsC92cB2qC9J9VtVT7YGLZiPlSETSoHgqJDT0C uphbo0wGbCA/RcbXmxtG+Ol3LCIDVnDWsYiqI5pt+tStR9YPJ3MTPfTxWouU8hyhROg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794458682; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=iaB2xZjkQsiHZeJLo1UomZRJ3RBDnszEW+eWkFRJiec=; b=Lu1+WYcK5FTa/i5UBA3+MNx88LTYyed1qNOVQLDO5g8NZZgiJ/iZ+JeLTo6o3JaegGjE zt3lmIXNRu2iNdKiXEXETHouQSlK2+if78LqBke3PHC4F499kdyfzi/VWeSCAG0ItxYj0 dUO2i86Rs6ayArSWhXdLlBma5/NGvA3VYHn+Zy2vnnxOccvM19BeaKyG5hy+ANkaqgrxs wQ0iDO2edtUkzwy70RVUVPpWS0QxrQxd29yxGbqgSFIR/82EfR2Mb6bW/+NRZJqzWRfM/ I5Hpcl2QvQLJFZV/yZwBZ5Y9u9pzNJ/f30FBkXeQau68dZ89VPhtC8LvhqSimgEsEBw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=l8sh7muA; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 17F67606A321 for ; Thu, 12 Nov 2026 04:44:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=l8sh7muA Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A0391F00A05; Thu, 12 Nov 2026 04:44:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794458681; bh=iaB2xZjkQsiHZeJLo1UomZRJ3RBDnszEW+eWkFRJiec=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=l8sh7muA/8ZhZRoNLSF9FgBcnH/2lEJbqrv2Rb2kSvcJZQqBnGnjIVnW2KSAUY1P8 y7xw+8Yqcn+ZAX91XSBG7MNdh3ki4/VksPr0szrAa9xtyfPh/G8I8ALeS+inJW0hsg RlVvP4f8KYS/OSKTChfgsOw4FwdSW77pU4EX26A/rJ16wyeApB/r03PsTScwN2om6F JjAmEbMffSaX9N4BkENsOG3df+qp4zBzX116Sa9BKL47oqGzsrUC2cg9q4/WA+dwDA hsyiUW4EHgq+xKKaVmuWgtyguzVHZtkbnGRTXwKKSs4JlmHjmWpdQAHcX4dM4a/3tZ Wm/n5+J38oioQ== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH RFC net v3 3/7] net/iucv: run recvmsg() under the socket lock Reply-To: sashiko-reviews@lists.linux.dev To: "Bryam Vargas" Cc: linux-s390@vger.kernel.org, "Heiko Carstens" , "Vasily Gorbik" , "Alexander Gordeev" , "Christian Borntraeger" In-Reply-To: <20261110-b4-disp-2a6b4364-v3-3-35677b68e697@proton.me> References: <20261110-b4-disp-2a6b4364-v3-0-35677b68e697@proton.me> <20261110-b4-disp-2a6b4364-v3-3-35677b68e697@proton.me> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 12 Nov 2026 04:44:41 +0000 X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Thank you for your contribution! Sashiko AI review found 1 potential issue to consider: - [Medium] net/iucv: missed shutdown wakeup in iucv_sock_sendmsg() during wmem wait -- commit 16ffdad8f70763ae645ac7eca51d7e6e91eed12b Author: Bryam Vargas net/iucv: run recvmsg() under the socket lock This commit acquires the socket lock in iucv_sock_recvmsg() while dropping = it in sk_wait_event() when waiting for data, and drops the socket lock in iucv_sock_sendmsg() while waiting for send buffer memory. Link: https://lore.kernel.org/all/20260724222917.134769-1-hexlabsecurity@pr= oton.me/ > diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c > index 133c1d1886b2a..639725917f3f8 100644 > --- a/net/iucv/af_iucv.c > +++ b/net/iucv/af_iucv.c > @@ -1041,7 +1041,17 @@ static int iucv_sock_sendmsg(struct socket *sock, = struct msghdr *msg, > } > } > skb =3D sock_alloc_send_pskb(sk, headroom + linear, len - linear, > - noblock, &err, 0); > + 1, &err, 0); > + if (!skb && err =3D=3D -EAGAIN && !noblock) { > + /* Wait without the socket lock: recvmsg() takes it, and over > + * z/VM the memory comes back only when the peer reads, which > + * may wait for our own reader. > + */ > + release_sock(sk); > + skb =3D sock_alloc_send_pskb(sk, headroom + linear, > + len - linear, 0, &err, 0); > + lock_sock(sk); > + } [Severity: Medium] Can a writer waiting in sock_alloc_send_pskb() without lock_sock(sk) miss a concurrent shutdown(SHUT_WR) wakeup when iucv_send_ctrl() temporarily clears SEND_SHUTDOWN? net/iucv/af_iucv.c:iucv_send_ctrl() { ... if (sk->sk_shutdown & SEND_SHUTDOWN) { /* controlling flags should be sent anyway */ shutdown =3D sk->sk_shutdown; sk->sk_shutdown &=3D RCV_SHUTDOWN; } skb =3D sock_alloc_send_skb(sk, blen, 1, &err); if (skb) { skb_reserve(skb, blen); err =3D afiucv_hs_send(NULL, sk, skb, flags); } if (shutdown) sk->sk_shutdown =3D shutdown; ... } Because sock_wait_for_wmem() now runs unlocked, it can race with iucv_send_ctrl() (called under lock_sock(sk) by iucv_sock_recvmsg() for a window update): CPU0 CPU1 iucv_sock_sendmsg() release_sock(sk) sock_alloc_send_pskb() sock_wait_for_wmem() prepare_to_wait(...) iucv_sock_shutdown(SHUT_WR) sk->sk_shutdown |=3D SEND_SHUTDOWN sk->sk_state_change(sk) iucv_sock_recvmsg() iucv_send_ctrl() sk->sk_shutdown &=3D RCV_SHUTDOWN if (sk->sk_shutdown & SEND_SHUTDOWN) /* false */ sk->sk_shutdown =3D shutdown schedule_timeout(timeo) <-- sleeps despite SHUT_WR Since iucv_send_ctrl() restores SEND_SHUTDOWN without waking sk_sleep(sk), iucv_sock_sendmsg() stays blocked in schedule_timeout() until send memory is freed or SO_SNDTIMEO expires instead of returning -EPIPE immediately. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261110-b4-disp-2a= 6b4364-v3-0-35677b68e697@proton.me?part=3D3