vfs: Don't let __fdget_pos() get FMODE_PATH files

Commit bd2a31d ("get rid of fget_light()") introduced the __fdget_pos() function, which returns the resulting file pointer and fdput flags combined in an 'unsigned long'. However, it also changed the behavior to return files with FMODE_PATH set, which shouldn't happen because read(), write(), lseek(), etc. aren't allowed on such files. This commit restores the old behavior. This regression actually had no effect on read() and write() since FMODE_READ and FMODE_WRITE are not set on file descriptors opened with O_PATH, but it did cause lseek() on a file descriptor opened with O_PATH to fail with ESPIPE rather than EBADF. Signed-off-by: Eric Biggers <[email protected]> Signed-off-by: Al Viro <[email protected]>
sum-it · Mar 23, 2014 · 99aea68 · 99aea68
1 parent d7a15f8
commit 99aea68
Showing 1 changed file with 4 additions and 15 deletions.
diff --git a/fs/file.c b/fs/file.c
@@ -713,27 +713,16 @@ unsigned long __fdget_raw(unsigned int fd)
 
 unsigned long __fdget_pos(unsigned int fd)
 {
-	struct files_struct *files = current->files;
-	struct file *file;
-	unsigned long v;
-
-	if (atomic_read(&files->count) == 1) {
-		file = __fcheck_files(files, fd);
-		v = 0;
-	} else {
-		file = __fget(fd, 0);
-		v = FDPUT_FPUT;
-	}
-	if (!file)
-		return 0;
+	unsigned long v = __fdget(fd);
+	struct file *file = (struct file *)(v & ~3);
 
-	if (file->f_mode & FMODE_ATOMIC_POS) {
+	if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
 		if (file_count(file) > 1) {
 			v |= FDPUT_POS_UNLOCK;
 			mutex_lock(&file->f_pos_lock);
 		}
 	}
-	return v | (unsigned long)file;
+	return v;
 }
 
 /*