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

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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: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2011-03-13 15:56:26 -04:00
parent bcda76524c
commit 65cfc67223
2 changed files with 11 additions and 6 deletions
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10
fs/open.c
View File

@ -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);

7
fs/stat.c
View File

@ -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;