[PATCH] tty/vt: don't set font mappings on vc not supporting this

[Sudip Mukherjee <sudipm.mukherjee@gmail.com>]

commit 9e326f78713a4421fe11afc2ddeac07698fac131 upstream

We can call this function for a dummy console that doesn't support
setting the font mapping, which will result in a null ptr BUG. So check
for this case and return error for consoles w/o font mapping support.

Cc: <stable@vger.kernel.org> # 3.14.x
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
---

backporting for the first time so not exactly sure if the format is ok.

 drivers/tty/vt/consolemap.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
index 2978ca5..08d36e4 100644
--- a/drivers/tty/vt/consolemap.c
+++ b/drivers/tty/vt/consolemap.c
@@ -540,6 +540,11 @@ int con_set_unimap(struct vc_data *vc, ushort ct, struct unipair __user *list)
 
 	/* Save original vc_unipagdir_loc in case we allocate a new one */
 	p = (struct uni_pagedir *)*vc->vc_uni_pagedir_loc;
+
+	if (!p) {
+		err = -EINVAL;
+		goto out_unlock;
+	}
 	if (p->readonly) {
 		console_unlock();
 		return -EIO;
@@ -633,6 +638,7 @@ int con_set_unimap(struct vc_data *vc, ushort ct, struct unipair __user *list)
 		set_inverse_transl(vc, p, i); /* Update inverse translations */
 	set_inverse_trans_unicode(vc, p);
 
+out_unlock:
 	console_unlock();
 	return err;
 }
-- 
1.9.1