[PATCH 4.4 338/342] security: let security modules use PTRACE_MODE_* with bitmasks

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jann Horn <redacted>

commit 3dfb7d8cdbc7ea0c2970450e60818bb3eefbad69 upstream.

It looks like smack and yama weren't aware that the ptrace mode
can have flags ORed into it - PTRACE_MODE_NOAUDIT until now, but
only for /proc/$pid/stat, and with the PTRACE_MODE_*CREDS patch,
all modes have flags ORed into them.

Signed-off-by: Jann Horn <redacted>
Acked-by: Kees Cook <redacted>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Morris <redacted>
Cc: "Serge E. Hallyn" <redacted>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W. Biederman" <redacted>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 security/smack/smack_lsm.c |    8 +++-----
 security/yama/yama_lsm.c   |    4 ++--
 2 files changed, 5 insertions(+), 7 deletions(-)

--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c

@@ -398,12 +398,10 @@ static int smk_copy_relabel(struct list_
  */
 static inline unsigned int smk_ptrace_mode(unsigned int mode)
 {
-	switch (mode) {
-	case PTRACE_MODE_READ:
-		return MAY_READ;
-	case PTRACE_MODE_ATTACH:
+	if (mode & PTRACE_MODE_ATTACH)
 		return MAY_READWRITE;
-	}
+	if (mode & PTRACE_MODE_READ)
+		return MAY_READ;
 
 	return 0;
 }
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c

@@ -281,7 +281,7 @@ static int yama_ptrace_access_check(stru
 	int rc = 0;
 
 	/* require ptrace target be a child of ptracer on attach */
-	if (mode == PTRACE_MODE_ATTACH) {
+	if (mode & PTRACE_MODE_ATTACH) {
 		switch (ptrace_scope) {
 		case YAMA_SCOPE_DISABLED:
 			/* No additional restrictions. */

@@ -307,7 +307,7 @@ static int yama_ptrace_access_check(stru
 		}
 	}
 
-	if (rc) {
+	if (rc && (mode & PTRACE_MODE_NOAUDIT) == 0) {
 		printk_ratelimited(KERN_NOTICE
 			"ptrace of pid %d was attempted by: %s (pid %d)\n",
 			child->pid, current->comm, current->pid);