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 X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 31833C28CC2 for ; Fri, 31 May 2019 19:23:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 10E6526E28 for ; Fri, 31 May 2019 19:23:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727326AbfEaTXz (ORCPT ); Fri, 31 May 2019 15:23:55 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:43664 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727242AbfEaTXw (ORCPT ); Fri, 31 May 2019 15:23:52 -0400 Received: by mail-pf1-f194.google.com with SMTP id c6so6766390pfa.10 for ; Fri, 31 May 2019 12:23:52 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding:cc:from:to; bh=jkiS8/qpTY6k4aMdDFBf1DTvMrA5045OTYV2nSZG2vg=; b=O0r4P6xSpLpSVlXlPfhdofNuSjpc0A7+xEUp8Jg9wudZdIOQNcDTbmvpiKUphw7xuj Fu4eV4ccenYLAir5cDZ5KGREgD7JhFBcGFLPpbWNmydXt2KAo0bg5fswYI9Eb3gZl3He MVFNe3zIIxR2w0hqjLu3NcBJpLvwwk+y2Tu+I+PNzcw545afTmBpnDIZvcfrjg1aez2P fduJ9yWGpnu1/Kq5ZDx7Qi4Fn1Rqk7f8GIN2CgzUoTZh5qgfTZIpwsHE7uH6MhG80p4x GIBaFIAk1qmN5bz4CbNo6+SBytUIiDqAc/hV7OyLwNBWqPM0Yg2LXY3T/b+9ve+EYpC/ QP8g== X-Gm-Message-State: APjAAAX/83ARnhWOeNAot8t23+B4QE39+3saWcSNJtLbAM9HptJP00nL LxpTEnhFvSb0SpTg2kOAy9gSqw== X-Google-Smtp-Source: APXvYqzOAHJ0yUdwkya1vFOdq3ZwH6YKGgpG1m54T+h5FGeOO4XVr55bLfMFMFpkBP4Vym1mdvxJ/A== X-Received: by 2002:a17:90a:c58b:: with SMTP id l11mr11650722pjt.56.1559330631558; Fri, 31 May 2019 12:23:51 -0700 (PDT) Received: from localhost ([12.206.222.5]) by smtp.gmail.com with ESMTPSA id s2sm7286629pfe.105.2019.05.31.12.23.50 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 31 May 2019 12:23:51 -0700 (PDT) Subject: [PATCH 2/5] Add fchmodat4(), a new syscall Date: Fri, 31 May 2019 12:12:01 -0700 Message-Id: <20190531191204.4044-3-palmer@sifive.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190531191204.4044-1-palmer@sifive.com> References: <20190531191204.4044-1-palmer@sifive.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: linux-arch@vger.kernel.org, x86@kernel.org, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, Arnd Bergmann , Palmer Dabbelt From: Palmer Dabbelt To: viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org man 3p says that fchmodat() takes a flags argument, but the Linux syscall does not. There doesn't appear to be a good userspace workaround for this issue but the implementation in the kernel is pretty straight-forward. The specific use case where the missing flags came up was WRT a fuse filesystem implemenation, but the functionality is pretty generic so I'm assuming there would be other use cases. Signed-off-by: Palmer Dabbelt --- fs/open.c | 21 +++++++++++++++++++-- include/linux/syscalls.h | 5 +++++ 2 files changed, 24 insertions(+), 2 deletions(-) diff --git a/fs/open.c b/fs/open.c index a00350018a47..cfad7684e8d3 100644 --- a/fs/open.c +++ b/fs/open.c @@ -568,11 +568,17 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) return ksys_fchmod(fd, mode); } -int do_fchmodat(int dfd, const char __user *filename, umode_t mode) +int do_fchmodat4(int dfd, const char __user *filename, umode_t mode, int flags) { struct path path; int error; - unsigned int lookup_flags = LOOKUP_FOLLOW; + unsigned int lookup_flags; + + if (unlikely(flags & ~AT_SYMLINK_NOFOLLOW)) + return -EINVAL; + + lookup_flags = flags & AT_SYMLINK_NOFOLLOW ? 0 : LOOKUP_FOLLOW; + retry: error = user_path_at(dfd, filename, lookup_flags, &path); if (!error) { @@ -586,6 +592,17 @@ int do_fchmodat(int dfd, const char __user *filename, umode_t mode) return error; } +SYSCALL_DEFINE4(fchmodat4, int, dfd, const char __user *, filename, + umode_t, mode, int, flags) +{ + return do_fchmodat4(dfd, filename, mode, flags); +} + +int do_fchmodat(int dfd, const char __user *filename, umode_t mode) +{ + return do_fchmodat4(dfd, filename, mode, 0); +} + SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode) { diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 396871b218f4..cb040a412a4c 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -435,6 +435,8 @@ asmlinkage long sys_chroot(const char __user *filename); asmlinkage long sys_fchmod(unsigned int fd, umode_t mode); asmlinkage long sys_fchmodat(int dfd, const char __user *filename, umode_t mode); +asmlinkage long sys_fchmodat4(int dfd, const char __user *filename, + umode_t mode, int flags); asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group, int flag); asmlinkage long sys_fchown(unsigned int fd, uid_t user, gid_t group); @@ -1315,6 +1317,9 @@ static inline long ksys_link(const char __user *oldname, extern int do_fchmodat(int dfd, const char __user *filename, umode_t mode); +extern int do_fchmodat4(int dfd, const char __user *filename, umode_t mode, + int flags); + static inline int ksys_chmod(const char __user *filename, umode_t mode) { return do_fchmodat(AT_FDCWD, filename, mode); -- 2.21.0