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>

1 files changed, 8 insertions, 5 deletions

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index b8b2498f57af..935f1c207a1f 100644
--- 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);
         }