Using the fs-interal do_fchownat() wrapper allows us to get rid of
fs-internal calls to the sys_fchownat() syscall.
Introducing the ksys_fchown() helper and the ksys_{,}chown() wrappers
allows us to avoid the in-kernel calls to the sys_{,l,f}chown() syscalls.
The ksys_ prefix denotes that these functions are meant as a drop-in
replacement for the syscalls. In particular, they use the same calling
convention as sys_{,l,f}chown().
This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
---
arch/s390/kernel/compat_linux.c | 6 +++---
fs/internal.h | 2 ++
fs/open.c | 23 +++++++++++++++++------
include/linux/syscalls.h | 17 +++++++++++++++++
init/initramfs.c | 8 ++++----
kernel/uid16.c | 6 +++---
6 files changed, 46 insertions(+), 16 deletions(-)
diff --git a/arch/s390/kernel/compat_linux.c b/arch/s390/kernel/compat_linux.c
index 5a9cfde5fc28..9a9bb395359c 100644
--- a/arch/s390/kernel/compat_linux.c
+++ b/arch/s390/kernel/compat_linux.c
@@ -89,18 +89,18 @@
COMPAT_SYSCALL_DEFINE3(s390_chown16, const char __user *, filename,
u16, user, u16, group)
{
- return sys_chown(filename, low2highuid(user), low2highgid(group));
+ return ksys_chown(filename, low2highuid(user), low2highgid(group));
}
COMPAT_SYSCALL_DEFINE3(s390_lchown16, const char __user *,
filename, u16, user, u16, group)
{
- return sys_lchown(filename, low2highuid(user), low2highgid(group));
+ return ksys_lchown(filename, low2highuid(user), low2highgid(group));
}
COMPAT_SYSCALL_DEFINE3(s390_fchown16, unsigned int, fd, u16, user, u16, group)
{
- return sys_fchown(fd, low2highuid(user), low2highgid(group));
+ return ksys_fchown(fd, low2highuid(user), low2highgid(group));
}
COMPAT_SYSCALL_DEFINE2(s390_setregid16, u16, rgid, u16, egid)
diff --git a/fs/internal.h b/fs/internal.h
index 26f4f05b52ef..c797480cbd6f 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -121,6 +121,8 @@ extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
long do_faccessat(int dfd, const char __user *filename, int mode);
int do_fchmodat(int dfd, const char __user *filename, umode_t mode);
+int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
+ int flag);
extern int open_check_o_direct(struct file *f);
extern int vfs_open(const struct path *, struct file *, const struct cred *);
diff --git a/fs/open.c b/fs/open.c
index 0fc8188be31a..7b2eccb541f2 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -645,8 +645,8 @@ static int chown_common(const struct path *path, uid_t user, gid_t group)
return error;
}
-SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
- gid_t, group, int, flag)
+int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
+ int flag)
{
struct path path;
int error = -EINVAL;
@@ -677,18 +677,24 @@ SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
return error;
}
+SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
+ gid_t, group, int, flag)
+{
+ return do_fchownat(dfd, filename, user, group, flag);
+}
+
SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
{
- return sys_fchownat(AT_FDCWD, filename, user, group, 0);
+ return do_fchownat(AT_FDCWD, filename, user, group, 0);
}
SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
{
- return sys_fchownat(AT_FDCWD, filename, user, group,
- AT_SYMLINK_NOFOLLOW);
+ return do_fchownat(AT_FDCWD, filename, user, group,
+ AT_SYMLINK_NOFOLLOW);
}
-SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
+int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
{
struct fd f = fdget(fd);
int error = -EBADF;
@@ -708,6 +714,11 @@ SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
return error;
}
+SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
+{
+ return ksys_fchown(fd, user, group);
+}
+
int open_check_o_direct(struct file *f)
{
/* NB: we're sure to have correct a_ops only after f_op->open */
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 33f06de090ea..df0d1e818a6e 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -954,6 +954,7 @@ int ksys_chroot(const char __user *filename);
ssize_t ksys_write(unsigned int fd, const char __user *buf, size_t count);
int ksys_chdir(const char __user *filename);
int ksys_fchmod(unsigned int fd, umode_t mode);
+int ksys_fchown(unsigned int fd, uid_t user, gid_t group);
/*
* The following kernel syscall equivalents are just wrappers to fs-internal
@@ -1021,4 +1022,20 @@ static inline long ksys_access(const char __user *filename, int mode)
return do_faccessat(AT_FDCWD, filename, mode);
}
+extern int do_fchownat(int dfd, const char __user *filename, uid_t user,
+ gid_t group, int flag);
+
+static inline long ksys_chown(const char __user *filename, uid_t user,
+ gid_t group)
+{
+ return do_fchownat(AT_FDCWD, filename, user, group, 0);
+}
+
+static inline long ksys_lchown(const char __user *filename, uid_t user,
+ gid_t group)
+{
+ return do_fchownat(AT_FDCWD, filename, user, group,
+ AT_SYMLINK_NOFOLLOW);
+}
+
#endif
diff --git a/init/initramfs.c b/init/initramfs.c
index 16c3c23076e2..35173bef7c00 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -343,7 +343,7 @@ static int __init do_name(void)
wfd = sys_open(collected, openflags, mode);
if (wfd >= 0) {
- sys_fchown(wfd, uid, gid);
+ ksys_fchown(wfd, uid, gid);
ksys_fchmod(wfd, mode);
if (body_len)
sys_ftruncate(wfd, body_len);
@@ -353,14 +353,14 @@ static int __init do_name(void)
}
} else if (S_ISDIR(mode)) {
ksys_mkdir(collected, mode);
- sys_chown(collected, uid, gid);
+ ksys_chown(collected, uid, gid);
ksys_chmod(collected, mode);
dir_add(collected, mtime);
} else if (S_ISBLK(mode) || S_ISCHR(mode) ||
S_ISFIFO(mode) || S_ISSOCK(mode)) {
if (maybe_link() == 0) {
ksys_mknod(collected, mode, rdev);
- sys_chown(collected, uid, gid);
+ ksys_chown(collected, uid, gid);
ksys_chmod(collected, mode);
do_utime(collected, mtime);
}
@@ -393,7 +393,7 @@ static int __init do_symlink(void)
collected[N_ALIGN(name_len) + body_len] = '\0';
clean_path(collected, 0);
ksys_symlink(collected + N_ALIGN(name_len), collected);
- sys_lchown(collected, uid, gid);
+ ksys_lchown(collected, uid, gid);
do_utime(collected, mtime);
state = SkipIt;
next_state = Reset;
diff --git a/kernel/uid16.c b/kernel/uid16.c
index 7b930edfe461..af6925d8599b 100644
--- a/kernel/uid16.c
+++ b/kernel/uid16.c
@@ -22,17 +22,17 @@
SYSCALL_DEFINE3(chown16, const char __user *, filename, old_uid_t, user, old_gid_t, group)
{
- return sys_chown(filename, low2highuid(user), low2highgid(group));
+ return ksys_chown(filename, low2highuid(user), low2highgid(group));
}
SYSCALL_DEFINE3(lchown16, const char __user *, filename, old_uid_t, user, old_gid_t, group)
{
- return sys_lchown(filename, low2highuid(user), low2highgid(group));
+ return ksys_lchown(filename, low2highuid(user), low2highgid(group));
}
SYSCALL_DEFINE3(fchown16, unsigned int, fd, old_uid_t, user, old_gid_t, group)
{
- return sys_fchown(fd, low2highuid(user), low2highgid(group));
+ return ksys_fchown(fd, low2highuid(user), low2highgid(group));
}
SYSCALL_DEFINE2(setregid16, old_gid_t, rgid, old_gid_t, egid)
--
2.16.3
