linux-kernel - [ 48/48] vfs: make O_PATH file descriptors usable for fchdir()

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Message-Id: <20120709143123.494694140@decadent.org.uk>
Date:	Mon, 09 Jul 2012 15:32:04 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	ÐŸÐ»ÑÐ³Ð° ÐºÑÑÐ¶Ð°ÐœÐŸÐ²ÑÐºÐ°Ñ 
	<olga.kryzhanovska@...il.com>, Al Viro <viro@...iv.linux.org.uk>
Subject: [ 48/48] vfs: make O_PATH file descriptors usable for fchdir()

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

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

From: Linus Torvalds <torvalds@...ux-foundation.org>

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 <olga.kryzhanovska@...il.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/open.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index d6c79a0..1540632 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -397,10 +397,10 @@ 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;
 
@@ -414,7 +414,7 @@ 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;
 }


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