linux-kernel - [PATCH v2 5/9] procfs: make /proc entries that use seq files able to access file->f

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Message-Id: <1380659178-28605-6-git-send-email-tixxdz@opendz.org>
Date:	Tue,  1 Oct 2013 21:26:14 +0100
From:	Djalal Harouni <tixxdz@...ndz.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Kees Cook <keescook@...omium.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	David Rientjes <rientjes@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org, kernel-hardening@...ts.openwall.com
Cc:	tixxdz@...il.com, Djalal Harouni <tixxdz@...ndz.org>
Subject: [PATCH v2 5/9] procfs: make /proc entries that use seq files able to access file->f_cred

In order to check if the cred of current have changed between ->open()
and ->read(), we must able to access the file's opener cred
'file->f_cred' at any point.

To make this possible for /proc/*/{stack,personality,stat} pass the
'file struct' as a 3rd argument to single_open() so it will be stored in
seq_file->private in seq_open(). This way these entries are able to
continue to use seq files, and access the file->f_cred easily.

This is also a preparation for the following patches which will check
the corresponding file->f_cred.

Signed-off-by: Djalal Harouni <tixxdz@...ndz.org>
---
 fs/proc/base.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 54e926a..d4b604d 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -765,7 +765,8 @@ static const struct file_operations proc_info_file_operations = {
 
 static int proc_single_show(struct seq_file *m, void *v)
 {
-	struct inode *inode = m->private;
+	struct file *filp = m->private;
+	struct inode *inode = file_inode(filp);
 	struct pid_namespace *ns;
 	struct pid *pid;
 	struct task_struct *task;
@@ -785,7 +786,9 @@ static int proc_single_show(struct seq_file *m, void *v)
 
 static int proc_single_open(struct inode *inode, struct file *filp)
 {
-	return single_open(filp, proc_single_show, inode);
+	/* Later we need inode and filp->f_cred, so pass filp as 3rd
+	 * argument, it will be referenced by seq_file->private */
+	return single_open(filp, proc_single_show, filp);
 }
 
 static const struct file_operations proc_single_file_operations = {
-- 
1.7.11.7

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