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Date: Wed, 25 Sep 2013 21:14:41 +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>,
	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 08/12] procfs: add permission checks on the file's opener of /proc/*/personality

If current's cred have changed between ->open() and ->read(), then call
proc_allow_access() to check if the original file's opener had enough
permissions to access the /proc/*/personality entry during ->read().

Cc: Kees Cook <keescook@...omium.org>
Cc: Eric W. Biederman <ebiederm@...ssion.com>
Signed-off-by: Djalal Harouni <tixxdz@...ndz.org>
---
 fs/proc/base.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index d6a17b3..ed8e3f7 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2656,11 +2656,21 @@ static const struct file_operations proc_projid_map_operations = {
 static int proc_pid_personality(struct seq_file *m, struct pid_namespace *ns,
 				struct pid *pid, struct task_struct *task)
 {
+	const struct cred *fcred = seq_f_cred(m);
+	int same_cred = proc_same_open_cred(fcred);
 	int err = lock_trace(task);
-	if (!err) {
-		seq_printf(m, "%08x\n", task->personality);
-		unlock_trace(task);
+	if (err)
+		return err;
+
+	if (!same_cred &&
+	    !proc_allow_access(fcred, task, PTRACE_MODE_ATTACH)) {
+		err = -EPERM;
+		goto out;
 	}
+
+	seq_printf(m, "%08x\n", task->personality);
+out:
+	unlock_trace(task);
 	return err;
 }
 
-- 
1.7.11.7

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