tty: Fix abusers of current->sighand->tty

Various people outside the tty layer still stick their noses in behind the
scenes. We need to make sure they also obey the locking and referencing rules.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 5 insertions, 6 deletions

diff --git a/kernel/acct.c b/kernel/acct.c
index dd68b9059418..f6006a60df5d 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -548,7 +548,7 @@ static void do_acct_process(struct bsd_acct_struct *acct,
 #endif
 
         spin_lock_irq(&current->sighand->siglock);
-        tty = current->signal->tty;
+        tty = current->signal->tty;     /* Safe as we hold the siglock */
         ac.ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
         ac.ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
         ac.ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 59cedfb040e7..cf5bc2f5f9c3 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -246,8 +246,8 @@ static int audit_match_perm(struct audit_context *ctx, int mask)
         unsigned n;
         if (unlikely(!ctx))
                 return 0;
-
         n = ctx->major;
+
         switch (audit_classify_syscall(ctx->arch, n)) {
         case 0: /* native */
                 if ((mask & AUDIT_PERM_WRITE) &&
@@ -1204,13 +1204,13 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
                                  (context->return_valid==AUDITSC_SUCCESS)?"yes":"no",
                                  context->return_code);
 
-        mutex_lock(&tty_mutex);
-        read_lock(&tasklist_lock);
+        spin_lock_irq(&tsk->sighand->siglock);
         if (tsk->signal && tsk->signal->tty && tsk->signal->tty->name)
                 tty = tsk->signal->tty->name;
         else
                 tty = "(none)";
-        read_unlock(&tasklist_lock);
+        spin_unlock_irq(&tsk->sighand->siglock);
+
         audit_log_format(ab,
                   " a0=%lx a1=%lx a2=%lx a3=%lx items=%d"
                   " ppid=%d pid=%d auid=%u uid=%u gid=%u"
@@ -1230,7 +1230,6 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
                   context->egid, context->sgid, context->fsgid, tty,
                   tsk->sessionid);
 
-        mutex_unlock(&tty_mutex);
 
         audit_log_task_info(ab, tsk);
         if (context->filterkey) {