pipe_rdwr_fasync: fix the error handling to prevent the leak/crash

If the second fasync_helper() fails, pipe_rdwr_fasync() returns the error
but leaves the file on ->fasync_readers.

This was always wrong, but since 233e70f4228e78eb2f80dc6650f65d3ae3dbf17c
"saner FASYNC handling on file close" we have the new problem.  Because in
this case setfl() doesn't set FASYNC bit, __fput() will not do
->fasync(0), and we leak fasync_struct with ->fa_file pointing to the
freed file.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/pipe.c b/fs/pipe.c
index 3a48ba5179d55000e4d6b26f5a1eb7bfb5a5891d..14f502b89cf5c2eb46cf8f2fb476d055a7fb118a 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -699,12 +699,12 @@ pipe_rdwr_fasync(int fd, struct file *filp, int on)
        int retval;
 
        mutex_lock(&inode->i_mutex);
-
        retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
-
-       if (retval >= 0)
+       if (retval >= 0) {
                retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
-
+               if (retval < 0) /* this can happen only if on == T */
+                       fasync_helper(-1, filp, 0, &pipe->fasync_readers);
+       }
        mutex_unlock(&inode->i_mutex);
 
        if (retval < 0)