ptrace: do not audit capability check when outputing /proc/pid/stat

Reading /proc/pid/stat of another process checks if one has ptrace permissions
on that process.  If one does have permissions it outputs some data about the
process which might have security and attack implications.  If the current
task does not have ptrace permissions the read still works, but those fields
are filled with inocuous (0) values.  Since this check and a subsequent denial
is not a violation of the security policy we should not audit such denials.

This can be quite useful to removing ptrace broadly across a system without
flooding the logs when ps is run or something which harmlessly walks proc.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Serge E. Hallyn <serge.hallyn@canonical.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 800f113bea66..a27e56ca41a4 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -127,8 +127,9 @@ extern void __ptrace_link(struct task_struct *child,
                           struct task_struct *new_parent);
 extern void __ptrace_unlink(struct task_struct *child);
 extern void exit_ptrace(struct task_struct *tracer);
-#define PTRACE_MODE_READ   1
-#define PTRACE_MODE_ATTACH 2
+#define PTRACE_MODE_READ        0x01
+#define PTRACE_MODE_ATTACH      0x02
+#define PTRACE_MODE_NOAUDIT     0x04
 /* Returns 0 on success, -errno on denial. */
 extern int __ptrace_may_access(struct task_struct *task, unsigned int mode);
 /* Returns true on success, false on denial. */