Commit 55731b3c authored by Dominik Brodowski's avatar Dominik Brodowski
Browse files

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

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: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent cbfe20f5

arch/s390/kernel/compat_linux.c

+3 −3
Original line number Diff line number Diff line
@@ -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)

fs/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -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 *);

fs/open.c

+17 −6
Original line number Diff line number Diff line
@@ -645,8 +645,8 @@ retry_deleg: 
	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 @@ out: 
	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,

	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 @@ out: 
	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 */

include/linux/syscalls.h

+17 −0
Original line number Diff line number Diff line
@@ -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

init/initramfs.c

+4 −4
Original line number Diff line number Diff line
@@ -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;

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