[PATCH v2 3/9] procfs: Document the proposed solution to protect procfs entries

[Djalal Harouni <tixxdz@opendz.org>]

Note the proposed solution to protect sensitive procfs entries as
code comment.

Cc: Kees Cook <keescook@chromium.org>
Suggested-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
---
 fs/proc/base.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index c29eeae..8d21316 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -102,6 +102,17 @@
  *
  *	The classic example of a problem is opening file descriptors
  *	in /proc for a task before it execs a suid executable.
+ *
+ * Solution for sensitive files:
+ *	At each system call: open(),read(),write()... Perform the
+ *	ptrace_may_access() check.
+ *
+ *	After open() and during each system call: read(),write()...
+ *	If the cred of current have changed then perform the
+ *	proc_allow_access() check after the ptrace_may_access() one.
+ *
+ *	This way we can determine if current has gained more privileges
+ *	by execs a suid executable.
  */
 
 struct pid_entry {
-- 
1.7.11.7