From mboxrd@z Thu Jan 1 00:00:00 1970 From: Palmer Dabbelt Subject: [PATCH v2 2/4] Add fchmodat4(), a new syscall Date: Tue, 16 Jul 2019 18:27:17 -0700 Message-ID: <20190717012719.5524-3-palmer@sifive.com> References: <20190717012719.5524-1-palmer@sifive.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190717012719.5524-1-palmer@sifive.com> Sender: linux-kernel-owner@vger.kernel.org To: viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org Cc: rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com, linux@armlinux.org.uk, catalin.marinas@arm.com, will@kernel.org, tony.luck@intel.com, fenghua.yu@intel.com, geert@linux-m68k.org, monstr@monstr.eu, ralf@linux-mips.org, paul.burton@mips.com, jhogan@kernel.org, James.Bottomley@HansenPartnership.com, deller@gmx.de, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, heiko.carstens@de.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, Arnd Bergmann , peterz@infradead.org, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, Palmer Dabbelt List-Id: linux-arch.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 | 20 ++++++++++++++++---- include/linux/syscalls.h | 7 +++++-- 2 files changed, 21 insertions(+), 6 deletions(-) diff --git a/fs/open.c b/fs/open.c index b5b80469b93d..2f72b4d6a2c1 100644 --- a/fs/open.c +++ b/fs/open.c @@ -569,11 +569,17 @@ 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) { @@ -587,15 +593,21 @@ 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); +} + SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode) { - return do_fchmodat(dfd, filename, mode); + return do_fchmodat4(dfd, filename, mode, 0); } SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode) { - return do_fchmodat(AT_FDCWD, filename, mode); + return do_fchmodat4(AT_FDCWD, filename, mode, 0); } static int chown_common(const struct path *path, uid_t user, gid_t group) diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index e1c20f1d0525..a4bde25ad264 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -433,6 +433,8 @@ 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); @@ -1320,11 +1322,12 @@ static inline long ksys_link(const char __user *oldname, return do_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); } -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); + return do_fchmodat4(AT_FDCWD, filename, mode, 0); } extern long do_faccessat(int dfd, const char __user *filename, int mode); -- 2.21.0 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f195.google.com ([209.85.214.195]:42361 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726466AbfGQB3P (ORCPT ); Tue, 16 Jul 2019 21:29:15 -0400 Received: by mail-pl1-f195.google.com with SMTP id ay6so11036558plb.9 for ; Tue, 16 Jul 2019 18:29:15 -0700 (PDT) Subject: [PATCH v2 2/4] Add fchmodat4(), a new syscall Date: Tue, 16 Jul 2019 18:27:17 -0700 Message-ID: <20190717012719.5524-3-palmer@sifive.com> In-Reply-To: <20190717012719.5524-1-palmer@sifive.com> References: <20190717012719.5524-1-palmer@sifive.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Palmer Dabbelt Sender: linux-arch-owner@vger.kernel.org List-ID: To: viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org Cc: rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com, linux@armlinux.org.uk, catalin.marinas@arm.com, will@kernel.org, tony.luck@intel.com, fenghua.yu@intel.com, geert@linux-m68k.org, monstr@monstr.eu, ralf@linux-mips.org, paul.burton@mips.com, jhogan@kernel.org, James.Bottomley@HansenPartnership.com, deller@gmx.de, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, heiko.carstens@de.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, Arnd Bergmann , peterz@infradead.org, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, Palmer Dabbelt , dhowells@redhat.com, firoz.khan@linaro.org, stefan@agner.ch, schwidefsky@de.ibm.com, axboe@kernel.dk, christian@brauner.io, hare@suse.com, deepa.kernel@gmail.com, tycho@tycho.ws, kim.phillips@arm.com, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org Message-ID: <20190717012717.iNC-t2ldhQegMS9azyFaH9nYnXKurjZRbH5mStnswJ0@z> 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 | 20 ++++++++++++++++---- include/linux/syscalls.h | 7 +++++-- 2 files changed, 21 insertions(+), 6 deletions(-) diff --git a/fs/open.c b/fs/open.c index b5b80469b93d..2f72b4d6a2c1 100644 --- a/fs/open.c +++ b/fs/open.c @@ -569,11 +569,17 @@ 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) { @@ -587,15 +593,21 @@ 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); +} + SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode) { - return do_fchmodat(dfd, filename, mode); + return do_fchmodat4(dfd, filename, mode, 0); } SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode) { - return do_fchmodat(AT_FDCWD, filename, mode); + return do_fchmodat4(AT_FDCWD, filename, mode, 0); } static int chown_common(const struct path *path, uid_t user, gid_t group) diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index e1c20f1d0525..a4bde25ad264 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -433,6 +433,8 @@ 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); @@ -1320,11 +1322,12 @@ static inline long ksys_link(const char __user *oldname, return do_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); } -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); + return do_fchmodat4(AT_FDCWD, filename, mode, 0); } extern long do_faccessat(int dfd, const char __user *filename, int mode); -- 2.21.0