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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 805A7EB64DC for ; Tue, 11 Jul 2023 16:18:48 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4R0mJl10xLz3gpH for ; Wed, 12 Jul 2023 02:18:47 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=softfail (domain owner discourages use of this host) smtp.mailfrom=kernel.org (client-ip=207.211.30.44; helo=us-smtp-delivery-44.mimecast.com; envelope-from=legion@kernel.org; receiver=lists.ozlabs.org) Received: from us-smtp-delivery-44.mimecast.com (unknown [207.211.30.44]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4R0mHF199pz3hP9 for ; Wed, 12 Jul 2023 02:17:28 +1000 (AEST) Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-287-zFqPIjk9Pg208y19fOqwOQ-1; Tue, 11 Jul 2023 12:17:19 -0400 X-MC-Unique: zFqPIjk9Pg208y19fOqwOQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B51E6185AD26; Tue, 11 Jul 2023 16:17:11 +0000 (UTC) Received: from localhost.localdomain.com (unknown [10.45.225.44]) by smtp.corp.redhat.com (Postfix) with ESMTP id 90838200AD6E; Tue, 11 Jul 2023 16:17:00 +0000 (UTC) From: Alexey Gladkov To: LKML , Arnd Bergmann , linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk Subject: [PATCH v4 2/5] fs: Add fchmodat2() Date: Tue, 11 Jul 2023 18:16:04 +0200 Message-Id: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: dalias@libc.org, linux-ia64@vger.kernel.org, fenghua.yu@intel.com, alexander.shishkin@linux.intel.com, Palmer Dabbelt , x86@kernel.org, stefan@agner.ch, ldv@altlinux.org, dhowells@redhat.com, kim.phillips@arm.com, paulus@samba.org, deepa.kernel@gmail.com, hpa@zytor.com, sparclinux@vger.kernel.org, will@kernel.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, hare@suse.com, ysato@users.sourceforge.jp, deller@gmx.de, linux-sh@vger.kernel.org, linux@armlinux.org.uk, borntraeger@de.ibm.com, mingo@redhat.com, geert@linux-m68k.org, catalin.marinas@arm.com, jhogan@kernel.org, mattst88@gmail.com, fweimer@redhat.com, gor@linux.ibm.com, glebfm@altlinux.org, tycho@tycho.ws, acme@kernel.org, linux-m68k@lists.linux-m68k.org, ink@jurassic.park.msu.ru, luto@kernel.org, namhyung@kernel.org, tglx@linutronix.de, christian@brauner.io, axboe@kernel.dk, James.Bottomley@HansenPartnership.com, monstr@monstr.eu, tony.luck@intel.com, linux-parisc@vger.kernel.org, linux-mips@ vger.kernel.org, ralf@linux-mips.org, peterz@infradead.org, linux-alpha@vger.kernel.org, bp@alien8.de, linuxppc-dev@lists.ozlabs.org, davem@davemloft.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On the userspace side fchmodat(3) is implemented as a wrapper function which implements the POSIX-specified interface. This interface differs from the underlying kernel system call, which does not have a flags argument. Most implementations require procfs [1][2]. There doesn't appear to be a good userspace workaround for this issue but the implementation in the kernel is pretty straight-forward. The new fchmodat2() syscall allows to pass the AT_SYMLINK_NOFOLLOW flag, unlike existing fchmodat. [1] https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/fchmodat.c;h=17eca54051ee28ba1ec3f9aed170a62630959143;hb=a492b1e5ef7ab50c6fdd4e4e9879ea5569ab0a6c#l35 [2] https://git.musl-libc.org/cgit/musl/tree/src/stat/fchmodat.c?id=718f363bc2067b6487900eddc9180c84e7739f80#n28 Co-developed-by: Palmer Dabbelt Signed-off-by: Palmer Dabbelt Signed-off-by: Alexey Gladkov Acked-by: Arnd Bergmann --- fs/open.c | 18 ++++++++++++++---- include/linux/syscalls.h | 2 ++ 2 files changed, 16 insertions(+), 4 deletions(-) diff --git a/fs/open.c b/fs/open.c index 0c55c8e7f837..39a7939f0d00 100644 --- a/fs/open.c +++ b/fs/open.c @@ -671,11 +671,11 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) return err; } -static int do_fchmodat(int dfd, const char __user *filename, umode_t mode) +static int do_fchmodat(int dfd, const char __user *filename, umode_t mode, int lookup_flags) { struct path path; int error; - unsigned int lookup_flags = LOOKUP_FOLLOW; + retry: error = user_path_at(dfd, filename, lookup_flags, &path); if (!error) { @@ -689,15 +689,25 @@ static int do_fchmodat(int dfd, const char __user *filename, umode_t mode) return error; } +SYSCALL_DEFINE4(fchmodat2, int, dfd, const char __user *, filename, + umode_t, mode, int, flags) +{ + if (unlikely(flags & ~AT_SYMLINK_NOFOLLOW)) + return -EINVAL; + + return do_fchmodat(dfd, filename, mode, + flags & AT_SYMLINK_NOFOLLOW ? 0 : LOOKUP_FOLLOW); +} + SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode) { - return do_fchmodat(dfd, filename, mode); + return do_fchmodat(dfd, filename, mode, LOOKUP_FOLLOW); } SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode) { - return do_fchmodat(AT_FDCWD, filename, mode); + return do_fchmodat(AT_FDCWD, filename, mode, LOOKUP_FOLLOW); } /* diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 584f404bf868..6e852279fbc3 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -440,6 +440,8 @@ 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_fchmodat2(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); -- 2.33.8