Could we include this in our kernel? vfs: make O_PATH file descriptors usable for fchdir()

[Michal Hlavinka]

Hi,

I was asked if we can add this patch to our kernel in Fedora.

It's for ability to open a directory with execute permission but without 
read permission.

Michal

-------- Original Message --------

Michal, can you ask the Fedora Linux kernel people to backport this
patch, please (this is going to be needed by both ksh93 and KDE4)?

Josh

---------- Forwarded message ----------
From: Greg KH 
Date: Thu, Jul 12, 2012 at 7:51 PM
Subject: [ 42/68] vfs: make O_PATH file descriptors usable for fchdir()
To: [e-mail], [e-mail]
Cc: [e-mail], [e-mail],
[e-mail], Al Viro

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Linus Torvalds

commit 332a2e1244bd08b9e3ecd378028513396a004a24 upstream.

We already use them for openat() and friends, but fchdir() also wants to
be able to use O_PATH file descriptors.  This should make it comparable
to the O_SEARCH of Solaris.  In particular, O_PATH allows you to access
(not-quite-open) a directory you don't have read persmission to, only
execute permission.

Noticed during development of multithread support for ksh93.

Reported-by: ольга крыжановская 
Cc: Al Viro 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

---
  fs/open.c |    6 +++---
  1 file changed, 3 insertions(+), 3 deletions(-)

--- a/fs/open.c
+++ b/fs/open.c
@@ -396,10 +396,10 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd
  {
         struct file *file;
         struct inode *inode;
-       int error;
+       int error, fput_needed;

error = -EBADF;
-       file = fget(fd);
+       file = fget_raw_light(fd, &fput_needed);
         if (!file)
                 goto out;

@@ -413,7 +413,7 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd
         if (!error)
                 set_fs_pwd(current->fs, &file->f_path);
  out_putf:
-       fput(file);
+       fput_light(file, fput_needed);
  out:
         return error;
  }

Josh