linux-kernel - [PATCH 3/9] proc: new proc_exec_id

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Date:	Sun, 11 Mar 2012 00:25:13 +0100
From:	Djalal Harouni <tixxdz@...ndz.org>
To:	linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Alexey Dobriyan <adobriyan@...il.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Vasiliy Kulikov <segoon@...nwall.com>,
	Kees Cook <keescook@...omium.org>,
	Solar Designer <solar@...nwall.com>,
	WANG Cong <xiyou.wangcong@...il.com>,
	James Morris <james.l.morris@...cle.com>,
	Oleg Nesterov <oleg@...hat.com>,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Greg KH <gregkh@...uxfoundation.org>,
	Ingo Molnar <mingo@...e.hu>, Stephen Wilson <wilsons@...rt.ca>,
	"Jason A. Donenfeld" <Jason@...c4.com>,
	Djalal Harouni <tixxdz@...ndz.org>
Subject: [PATCH 3/9] proc: new proc_exec_id_ok() helper function

proc_exec_id_ok() will be used for /proc/<pid>/* files checks to see if the
task's exec_id equals the exec_id of the proc_file_private struct.

Signed-off-by: Djalal Harouni <tixxdz@...ndz.org>
---
 fs/proc/internal.h |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index a8968f6..bed27a8 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -10,6 +10,7 @@
  */
 
 #include <linux/proc_fs.h>
+#include <linux/sched.h>
 
 extern struct proc_dir_entry proc_root;
 #ifdef CONFIG_PROC_SYSCTL
@@ -95,6 +96,25 @@ static inline int proc_fd(struct inode *inode)
 	return PROC_I(inode)->fd;
 }
 
+/**
+ * proc_exec_id_ok - check if the task's exec_id equals the exec_id of
+ * the proc_file_private.
+ * @task: Task struct to check against.
+ * @proc_private: The proc_file_private struct.
+ *
+ * Check if the exec_id of the two structs are equal. Use it to protect
+ * special procfs files when the fd is passed to a new execve (i.e. suid)
+ *
+ * It will be more effective if the check is delayed as mush as possible
+ * to avoid any new execve surprises especially if we are checking against
+ * target task's exec_id.
+ */
+static inline int proc_exec_id_ok(struct task_struct *task,
+				  struct proc_file_private *proc_priv)
+{
+	return task_exec_id_ok(task, proc_priv->exec_id);
+}
+
 struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *ino,
 		struct dentry *dentry);
 int proc_readdir_de(struct proc_dir_entry *de, struct file *filp, void *dirent,
-- 
1.7.1

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