From: Alexey Gladkov <legion@kernel.org>
To: LKML <linux-kernel@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org,
viro@zeniv.linux.org.uk
Cc: James.Bottomley@HansenPartnership.com, acme@kernel.org,
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Palmer Dabbelt <palmer@sifive.com>
Subject: [PATCH v4 2/5] fs: Add fchmodat2()
Date: Tue, 11 Jul 2023 18:16:04 +0200 [thread overview]
Message-ID: <f2a846ef495943c5d101011eebcf01179d0c7b61.1689092120.git.legion@kernel.org> (raw)
In-Reply-To: <cover.1689092120.git.legion@kernel.org>
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 <palmer@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
---
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
next prev parent reply other threads:[~2023-07-11 16:18 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-17 1:27 Add a new fchmodat4() syscall, v2 Palmer Dabbelt
2019-07-17 1:27 ` [PATCH v2 1/4] Non-functional cleanup of a "__user * filename" Palmer Dabbelt
2019-07-17 1:27 ` [PATCH v2 2/4] Add fchmodat4(), a new syscall Palmer Dabbelt
2019-07-17 1:48 ` Al Viro
2019-07-17 2:12 ` Palmer Dabbelt
2019-07-17 2:40 ` Rich Felker
2019-07-17 3:02 ` Al Viro
2019-07-17 1:27 ` [PATCH v2 3/4] arch: Register fchmodat4, usually as syscall 434 Palmer Dabbelt
2019-07-17 1:27 ` [PATCH v2 4/4] tools: Add fchmodat4 Palmer Dabbelt
2019-07-17 12:39 ` Arnaldo Carvalho de Melo
2020-06-09 13:52 ` Add a new fchmodat4() syscall, v2 Florian Weimer
2023-07-11 11:25 ` [PATCH v3 0/5] Add a new fchmodat4() syscall Alexey Gladkov
2023-07-11 11:25 ` [PATCH v3 1/5] Non-functional cleanup of a "__user * filename" Alexey Gladkov
2023-07-11 11:32 ` Arnd Bergmann
2023-07-11 11:25 ` [PATCH v3 2/5] fs: Add fchmodat4() Alexey Gladkov
2023-07-11 11:42 ` Arnd Bergmann
2023-07-11 11:52 ` Christian Brauner
2023-07-11 12:51 ` Alexey Gladkov
2023-07-11 14:01 ` Christian Brauner
2023-07-11 15:23 ` Alexey Gladkov
2023-07-11 12:28 ` Matthew Wilcox
2023-07-11 12:49 ` Alexey Gladkov
2023-07-11 11:25 ` [PATCH v3 3/5] arch: Register fchmodat4, usually as syscall 451 Alexey Gladkov
2023-07-11 11:31 ` Arnd Bergmann
2023-07-11 11:25 ` [PATCH v3 4/5] tools headers UAPI: Sync files changed by new fchmodat4 syscall Alexey Gladkov
2023-07-11 11:25 ` [PATCH v3 5/5] selftests: add fchmodat4(2) selftest Alexey Gladkov
2023-07-11 12:10 ` Florian Weimer
2023-07-11 13:38 ` Alexey Gladkov
2023-07-11 12:24 ` [PATCH v3 0/5] Add a new fchmodat4() syscall Florian Weimer
2023-07-11 15:14 ` Christian Brauner
2023-07-25 11:05 ` Alexey Gladkov
2023-07-25 12:05 ` Christian Brauner
2023-07-11 16:16 ` [PATCH v4 0/5] Add a new fchmodat2() syscall Alexey Gladkov
2023-07-11 16:16 ` [PATCH v4 1/5] Non-functional cleanup of a "__user * filename" Alexey Gladkov
2023-07-11 16:16 ` Alexey Gladkov [this message]
2023-07-11 17:05 ` [PATCH v4 2/5] fs: Add fchmodat2() Christian Brauner
2023-07-25 16:36 ` Aleksa Sarai
2023-07-26 13:45 ` Alexey Gladkov
2023-07-27 10:26 ` Christian Brauner
2023-07-27 17:12 ` Aleksa Sarai
2023-07-27 17:39 ` Aleksa Sarai
2023-07-28 8:43 ` David Laight
2023-07-28 18:42 ` dalias
2023-07-27 9:01 ` David Laight
2023-07-27 16:28 ` Andreas Schwab
2023-07-27 17:02 ` Christian Brauner
2023-07-27 17:13 ` dalias
2023-07-27 17:36 ` Christian Brauner
2023-07-27 16:31 ` dalias
2023-07-11 16:16 ` [PATCH v4 3/5] arch: Register fchmodat2, usually as syscall 452 Alexey Gladkov
2023-07-11 16:26 ` Arnd Bergmann
2023-07-25 7:16 ` Geert Uytterhoeven
2023-07-25 16:43 ` Aleksa Sarai
2023-07-27 10:37 ` Christian Brauner
2023-07-27 17:42 ` Aleksa Sarai
2023-07-11 16:16 ` [PATCH v4 4/5] tools headers UAPI: Sync files changed by new fchmodat2 syscall Alexey Gladkov
2023-07-11 17:19 ` Namhyung Kim
2023-07-11 17:23 ` Alexey Gladkov
2023-07-11 16:16 ` [PATCH v4 5/5] selftests: Add fchmodat2 selftest Alexey Gladkov
2023-07-11 17:36 ` (subset) [PATCH v4 0/5] Add a new fchmodat2() syscall Christian Brauner
2023-07-12 2:42 ` Rich Felker
2023-07-25 15:58 ` Add fchmodat2() - or add a more general syscall? David Howells
2023-07-25 16:10 ` Florian Weimer
2023-07-25 16:50 ` Aleksa Sarai
2023-07-25 18:39 ` David Howells
2023-07-25 18:44 ` Rich Felker
2023-07-26 13:30 ` Christian Brauner
2023-07-27 3:57 ` Eric Biggers
2023-07-27 10:27 ` Christian Brauner
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