[patch 1/2] audit: let userspace fully control TTY input auditing

Remove the code that automatically disables TTY input auditing in processes
that open TTYs when they have no other TTY open; this heuristic was
intended to automatically handle daemons, but it has false positives (e.g.
with sshd) that make it impossible to control TTY input auditing from a PAM
module.  With this patch, TTY input auditing is controlled from user-space
only.

On the other hand, not even for daemons does it make sense to audit "input"
from PTY masters; this data was produced by a program writing to the PTY
slave, and does not represent data entered by the user.

Signed-off-by: Miloslav Trmac <mitr@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 5 insertions, 54 deletions

diff --git a/drivers/char/tty_audit.c b/drivers/char/tty_audit.c
index caeedd12d494..6342b0534f4d 100644
--- a/drivers/char/tty_audit.c
+++ b/drivers/char/tty_audit.c
@@ -233,6 +233,10 @@ void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
         if (unlikely(size == 0))
                 return;
 
+        if (tty->driver->type == TTY_DRIVER_TYPE_PTY
+            && tty->driver->subtype == PTY_TYPE_MASTER)
+                return;
+
         buf = tty_audit_buf_get(tty);
         if (!buf)
                 return;
@@ -295,53 +299,3 @@ void tty_audit_push(struct tty_struct *tty)
                 tty_audit_buf_put(buf);
         }
 }
-
-/**
- *      tty_audit_opening       -       A TTY is being opened.
- *
- *      As a special hack, tasks that close all their TTYs and open new ones
- *      are assumed to be system daemons (e.g. getty) and auditing is
- *      automatically disabled for them.
- */
-void tty_audit_opening(void)
-{
-        int disable;
-
-        disable = 1;
-        spin_lock_irq(&current->sighand->siglock);
-        if (current->signal->audit_tty == 0)
-                disable = 0;
-        spin_unlock_irq(&current->sighand->siglock);
-        if (!disable)
-                return;
-
-        task_lock(current);
-        if (current->files) {
-                struct fdtable *fdt;
-                unsigned i;
-
-                /*
-                 * We don't take a ref to the file, so we must hold ->file_lock
-                 * instead.
-                 */
-                spin_lock(&current->files->file_lock);
-                fdt = files_fdtable(current->files);
-                for (i = 0; i < fdt->max_fds; i++) {
-                        struct file *filp;
-
-                        filp = fcheck_files(current->files, i);
-                        if (filp && is_tty(filp)) {
-                                disable = 0;
-                                break;
-                        }
-                }
-                spin_unlock(&current->files->file_lock);
-        }
-        task_unlock(current);
-        if (!disable)
-                return;
-
-        spin_lock_irq(&current->sighand->siglock);
-        current->signal->audit_tty = 0;
-        spin_unlock_irq(&current->sighand->siglock);
-}
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 4d3c7018f0c3..afddccf1bb3d 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -2755,7 +2755,6 @@ got_driver:
                 __proc_set_tty(current, tty);
         spin_unlock_irq(&current->sighand->siglock);
         mutex_unlock(&tty_mutex);
-        tty_audit_opening();
         return 0;
 }
 
@@ -2818,10 +2817,8 @@ static int ptmx_open(struct inode *inode, struct file *filp)
 
         check_tty_count(tty, "tty_open");
         retval = ptm_driver->open(tty, filp);
-        if (!retval) {
-                tty_audit_opening();
+        if (!retval)
                 return 0;
-        }
 out1:
         release_dev(filp);
         return retval;