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=1793831788; b=cpK9O+zRfe1l/E69PMrynhoiJcVAHQc73jeSIcFyIXkAfXFXAHVs7VSZ+kbISzjMYxRu JgSkUIa00dJ/aS4WCKMCBJ3cVd2DuXaCQQDQvx7XUSjaR8qZO57NH0elvoNBvNdS+SpG8 EiQ1sYfppsriI4/tJYOdpixPb4isbKJ902hXR5ZdWrb7u38uhSx6aZX2o378JhpLkRwa8 HIrNYebiMbo5yOk2/55cSp+Zx4S9Ia14yA4TRpr3Ce5YdIZoBXaS8c3Ze/IVYTCnbeUnf oNAVR58PDHcZfBeNgOmdGs1K8fOBABNWszYkFFVkoVphtbxaHs3TNLTcFJchr/FzYNg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793831788; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=0Zbvvn56wF49Yjg5NQ2fu65IXu29rzWhYGdeRyyCXJ4=; b=K3IqQbRn59LNhv/mQiPob/IQ/rPxh8gKh6C0XavH41EhNINk2ZL+jGcU8cxzAo/2Ry1N YIShLQn7w8iZ43O850+0bO2s2Wv2JHzfhAOHoRzR6bQr2CRPj5jqacrxTDyye4HAFKG7O ReK+hoQfYTYHyKpSL995s5j3ct8xslE4EDiOVlDdHfeb5l9VpSCSwuwBQhrrJ9RdwuL/I NXSAepPSQd1eVe1aHoANh720OeJYn8rtWteVLzyxefxq3JQ8YKMCw1zOUAOiyrJoFUwlF r2xOTF1aARPljpdYSaFCcPcDcpJeAzxrrsVjAiQkBIEyEMjuNHREvFH7T/71DrKgsTQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=t6XV+YTF; 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 B2A21606AC37; Wed, 4 Nov 2026 22:36:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=t6XV+YTF Received: by smtp.kernel.org (Postfix) with ESMTPSA id 095B51F000C1; Wed, 4 Nov 2026 22:36:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793831787; bh=0Zbvvn56wF49Yjg5NQ2fu65IXu29rzWhYGdeRyyCXJ4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=t6XV+YTFP6JGbGKgCViHukjTQhEqywIS7jOYHehp/+EY3ESWCgupFTJPOxlYSxzmn LWDmOh8q74lrBTMU7uw51ZdERy4ndcXNxkKBjTeMNPkwITZsXOyFUXRCS7BS/sBXFY o3othWpF+Yc/JGcmj3lkXPDhUs2ZXPGCUwdPhTOQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+54cdc566f64abf51b7f1@syzkaller.appspotmail.com, Jeff Layton , Chuck Lever Subject: [PATCH 6.18 0912/1005] SUNRPC: Reject a socket that already has an svc_sock attached Date: Wed, 4 Nov 2026 16:10:45 -0500 Message-ID: <20261104211108.711532275@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211043.516122098@linuxfoundation.org> References: <20261104211043.516122098@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chuck Lever commit 0995447b8059c4d23853cdcddbe789c4a2b6bb88 upstream. Writing the same socket descriptor to /proc/fs/nfsd/portlist twice attaches a second svc_sock to one socket. svc_setup_socket() saves the socket's callbacks before installing its own, so the second attach records svc_write_space() as the old write_space callback. svc_udp_init() invokes that callback by way of svc_sock_setbufsize(), and svc_write_space() then calls itself until the kernel stack is exhausted: BUG: TASK stack guard page was hit at ffffc900037d7ff8 svc_write_space+0x90/0x2b0 net/sunrpc/svcsock.c:429 svc_write_space+0xe6/0x2b0 net/sunrpc/svcsock.c:430 ... 700 more ... svc_sock_setbufsize+0x18d/0x220 net/sunrpc/svcsock.c:386 svc_udp_init net/sunrpc/svcsock.c:854 [inline] svc_setup_socket+0xb2f/0x1090 net/sunrpc/svcsock.c:1498 svc_addsock+0x2fd/0x760 net/sunrpc/svcsock.c:1547 __write_ports_addfd fs/nfsd/nfsctl.c:742 [inline] write_ports+0xa5b/0xcc0 fs/nfsd/nfsctl.c:861 nfsctl_transaction_write+0x106/0x1a0 fs/nfsd/nfsctl.c:112 svc_data_ready() and svc_tcp_state_change() chain through their saved callbacks the same way, so a TCP descriptor added twice recurses on the next incoming segment instead. Reaching any of this takes a writer on portlist, and the nfsd filesystem sets no FS_USERNS_MOUNT, so the reproducer needs CAP_SYS_ADMIN in the initial user namespace. Reject a socket that already carries sk_user_data. svc_setup_socket() overwrites that field unconditionally, so a socket some other consumer has claimed is one NFSD would corrupt whether or not the callbacks recurse. Fixes: b41b66d63c73 ("[PATCH] knfsd: allow sockets to be passed to nfsd via 'portlist'") Cc: stable@vger.kernel.org Reported-by: syzbot+54cdc566f64abf51b7f1@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=54cdc566f64abf51b7f1 Link: https://patch.msgid.link/20260815162844.8219-1-cel@kernel.org Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/svcsock.c | 3 +++ 1 file changed, 3 insertions(+) --- a/net/sunrpc/svcsock.c +++ b/net/sunrpc/svcsock.c @@ -1550,6 +1550,9 @@ int svc_addsock(struct svc_serv *serv, s err = -EISCONN; if (so->state > SS_UNCONNECTED) goto out; + err = -EBUSY; + if (so->sk->sk_user_data) + goto out; err = -ENOENT; if (!try_module_get(THIS_MODULE)) goto out;