vt: fix vc_resize locking

Lockdep says we can't take tasklist lock or sighand lock inside ctrl_lock.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Alan Cox <alan@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index b8b2498f57af64af0314be6caa5bbe998c0fa7ea..935f1c207a1f0edfe7056fee448e4ff337164229 100644 (file)
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -909,7 +909,7 @@ int vc_resize(struct vc_data *vc, unsigned int cols, unsigned int lines)
 
        if (vc->vc_tty) {
                struct winsize ws, *cws = &vc->vc_tty->winsize;
-               unsigned long flags;
+               struct pid *pgrp = NULL;
 
                memset(&ws, 0, sizeof(ws));
                ws.ws_row = vc->vc_rows;
@@ -917,11 +917,14 @@ int vc_resize(struct vc_data *vc, unsigned int cols, unsigned int lines)
                ws.ws_ypixel = vc->vc_scan_lines;
 
                mutex_lock(&vc->vc_tty->termios_mutex);
-               spin_lock_irqsave(&vc->vc_tty->ctrl_lock, flags);
-               if ((ws.ws_row != cws->ws_row || ws.ws_col != cws->ws_col) &&
-                   vc->vc_tty->pgrp)
+               spin_lock_irq(&vc->vc_tty->ctrl_lock);
+               if ((ws.ws_row != cws->ws_row || ws.ws_col != cws->ws_col))
+                       pgrp = get_pid(vc->vc_tty->pgrp);
+               spin_unlock_irq(&vc->vc_tty->ctrl_lock);
+               if (pgrp) {
                        kill_pgrp(vc->vc_tty->pgrp, SIGWINCH, 1);
-               spin_unlock_irqrestore(&vc->vc_tty->ctrl_lock, flags);
+                       put_pid(pgrp);
+               }
                *cws = ws;
                mutex_unlock(&vc->vc_tty->termios_mutex);
        }