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fs: add do_fchownat(), ksys_fchown() helpers and ksys_{,l}chown() wrappers

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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@light.dominikbrodowski.net

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
This commit is contained in:
Dominik Brodowski 2018-03-11 11:34:55 +01:00
parent cbfe20f565
commit 55731b3cda
6 changed files with 46 additions and 16 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
arch/s390/kernel/compat_linux.c
View file

@ -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)

2
fs/internal.h
View file

@ -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 *);

23
fs/open.c
View file

@ -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 */

17
include/linux/syscalls.h
View file

@ -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

8
init/initramfs.c
View file

@ -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;

6
kernel/uid16.c
View file

@ -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)