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Commit 65cfc672 authored by Al Viro's avatar Al Viro
Browse files

readlinkat(), fchownat() and fstatat() with empty relative pathnames 



For readlinkat() we simply allow empty pathname; it will fail unless
we have dfd equal to O_PATH-opened symlink, so we are outside of
POSIX scope here.  For fchownat() and fstatat() we allow AT_EMPTY_PATH;
let the caller explicitly ask for such behaviour.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent bcda7652

fs/open.c

+6 −4
Original line number Diff line number Diff line
@@ -573,13 +573,15 @@ SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user, 
{

	struct path path;

	int error = -EINVAL;

	int follow;

	int lookup_flags;



	if ((flag & ~AT_SYMLINK_NOFOLLOW) != 0)

	if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)

		goto out;



	follow = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;

	error = user_path_at(dfd, filename, follow, &path);

	lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;

	if (flag & AT_EMPTY_PATH)

		lookup_flags |= LOOKUP_EMPTY;

	error = user_path_at(dfd, filename, lookup_flags, &path);

	if (error)

		goto out;

	error = mnt_want_write(path.mnt);

fs/stat.c

+5 −2
Original line number Diff line number Diff line
@@ -75,13 +75,16 @@ int vfs_fstatat(int dfd, const char __user *filename, struct kstat *stat, 
	int error = -EINVAL;

	int lookup_flags = 0;



	if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT)) != 0)

	if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT |

		      AT_EMPTY_PATH)) != 0)

		goto out;



	if (!(flag & AT_SYMLINK_NOFOLLOW))

		lookup_flags |= LOOKUP_FOLLOW;

	if (flag & AT_NO_AUTOMOUNT)

		lookup_flags |= LOOKUP_NO_AUTOMOUNT;

	if (flag & AT_EMPTY_PATH)

		lookup_flags |= LOOKUP_EMPTY;



	error = user_path_at(dfd, filename, lookup_flags, &path);

	if (error)
@@ -297,7 +300,7 @@ SYSCALL_DEFINE4(readlinkat, int, dfd, const char __user *, pathname, 
	if (bufsiz <= 0)

		return -EINVAL;



	error = user_path_at(dfd, pathname, 0, &path);

	error = user_path_at(dfd, pathname, LOOKUP_EMPTY, &path);

	if (!error) {

		struct inode *inode = path.dentry->d_inode;