From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6506C43219 for ; Tue, 22 Nov 2022 16:16:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234343AbiKVQQU (ORCPT ); Tue, 22 Nov 2022 11:16:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42990 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234288AbiKVQP7 (ORCPT ); Tue, 22 Nov 2022 11:15:59 -0500 Received: from mail-wr1-x434.google.com (mail-wr1-x434.google.com [IPv6:2a00:1450:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7345D73431 for ; Tue, 22 Nov 2022 08:13:51 -0800 (PST) Received: by mail-wr1-x434.google.com with SMTP id b12so11661860wrn.2 for ; Tue, 22 Nov 2022 08:13:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=mC90GwNhm6j7BlWHBWFQA6hS+M8xqG7H71ScqSgu+SE=; b=duED85v80csEaRq1YyX8RGCan5YsZObsDE+LxOFw2hRKLd4y74hJ6VQpH2h8i42z3a Clii+1EG793oZfMdmFqoOXa6/ceHR4g9KwtXM/2o4kfpKIHEwQaVTAIE3wvAVwoB/32u wpVuAXugU8a9n8vANtU1W1XTMegemYjVCPGXndxhV8l1D/UznxvyXgXQ+8jCYydRJjfy 6nXiMTWxIdUjqfx/wRrvMOfOyJbyEsQyeEm+M9vEFOoKFpge1FaGl+okkjKZoQYH3F7y R6KCyvD+KFF3Khy2rvirDlDJOuYh1eJzSja6BYJgs7j42ubvK8GD5SxEcVe+FADW1PHF IUAw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=mC90GwNhm6j7BlWHBWFQA6hS+M8xqG7H71ScqSgu+SE=; b=Mw6FQgVD7ezAUM7+PXJ1mKe6M0K3IfgUG7LFXUckJXFY153TGkN1i/7heU7/jtqrxY G4U6Ok2t8w560G7CLgrbqZd5OWsi3eYV449fr6GTycvtDo67cIwUUyHlhJsg+SZXfnsd LtMq+4kTeG4z+n6G5wJ+GLbDr8KbRN4SAOL2btSYGd6zYby+HWS4aakImbW988TSZZdW Hta8wjkl9HJJy1lvWX8nRx11iQ52Gy5KNn8bfNCD8HAzghh/Qb9jvkCWhzbKpBoa1sse X2mLfia3WsQbUPBpv20Pxcw18PPiU4T1JLRho4RABIHSeMU0yOU3PgmiG6w/l0XSduNb tl/w== X-Gm-Message-State: ANoB5plEb5fuhB8bpa0aNiaPBhx4dWZ5lkXtxnwc7EgObXk9ayJyS4Eo Hpzkhu7QVSsNekJ4R0T7lYY= X-Google-Smtp-Source: AA0mqf5qnuuB7LLLd0XE2bXOYFU/xJz0C1TnyOb7qcwmV6QYY7frWdzVjqgcGPlabDwcunMKuQIgWg== X-Received: by 2002:adf:fb4c:0:b0:236:5270:735e with SMTP id c12-20020adffb4c000000b002365270735emr3949996wrs.659.1669133629782; Tue, 22 Nov 2022 08:13:49 -0800 (PST) Received: from localhost.localdomain (2001-1ae9-2f0-fa00-5962-fdfb-2a9a-17bd.ip6.tmcz.cz. [2001:1ae9:2f0:fa00:5962:fdfb:2a9a:17bd]) by smtp.googlemail.com with ESMTPSA id j13-20020adff54d000000b0023655e51c33sm14610846wrp.4.2022.11.22.08.13.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Nov 2022 08:13:48 -0800 (PST) From: Petr Skocik To: "Eric W. Biederman" Cc: Oleg Nesterov , Kees Cook , Thomas Gleixner , Peter Zijlstra , Marco Elver , linux-kernel@vger.kernel.org, Petr Skocik Subject: [PATCH 0/1] *** Fix kill(-1,s) returning 0 on 0 kills *** Date: Tue, 22 Nov 2022 17:12:40 +0100 Message-Id: <20221122161240.137570-1-pskocik@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi. I've never sent a kernel patch before but this one seemed trivial, so I thought I'd give it a shot. My issue: kill(-1,s) on Linux doesn't return -ESCHR when it has nothing to kill. The code sample below demonstrates the problem, which gets fixed by the patch: #define _GNU_SOURCE #include #include #include #include #include #include #define VICTIM_UID 4200 //check these are safe to use on your system! #define UNUSED_UID 4300 int main(){ uid_t r,e,s; if(geteuid()) return 1; //requires root privileges //pipe to let the parent know when the child has changed ids int fds[2]; if(0>pipe(fds)) return 1; pid_t pid; if(0>(pid=fork())) return 1; else if(0==pid){ setreuid(VICTIM_UID,VICTIM_UID); getresuid(&r,&e,&s); printf("child: %u %u %u\n", r,e,s); close(fds[0]); close(fds[1]); //let the parent continue for(;;) pause(); } close(fds[1]); read(fds[0],&(char){0},1); //wait for uid change in the child #if 1 setreuid(VICTIM_UID,(uid_t)-1); seteuid(VICTIM_UID); #else setresuid(UNUSED_UID,VICTIM_UID,0); #endif getresuid(&r,&e,&s); printf("parent: %u %u %u\n", r,e,s); //4200 4200 0 int err = kill(-1,-111); (void)err; //test -EINVAL assert(err < 0 && errno == EINVAL); int rc = kill(-1,SIGTERM); //test 0 if(rc>=0) wait(0); int rc2 = kill(-1,SIGTERM); //test -ESCHR printf("1st kill ok==%d; 2nd kill ESRCH==%d\n", rc==0, rc2<0&& errno==ESRCH); } Thank you for considering the patch. Best regards, Petr S. Petr Skocik (1): Fix kill(-1,s) returning 0 on 0 kills kernel/signal.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) -- 2.25.1