diff mbox series

tty: make FONTX ioctl use the tty pointer they were actually passed

Message ID 20210223145008.6968-2-tim.gardner@canonical.com
State New
Headers show
Series tty: make FONTX ioctl use the tty pointer they were actually passed | expand

Commit Message

Tim Gardner Feb. 23, 2021, 2:50 p.m. UTC 
From: Linus Torvalds <torvalds@linux-foundation.org>

commit 90bfdeef83f1d6c696039b6a917190dcbbad3220 upstream.

Some of the font tty ioctl's always used the current foreground VC for
their operations.  Don't do that then.

This fixes a data race on fg_console.

Side note: both Michael Ellerman and Jiri Slaby point out that all these
ioctls are deprecated, and should probably have been removed long ago,
and everything seems to be using the KDFONTOP ioctl instead.

In fact, Michael points out that it looks like busybox's loadfont
program seems to have switched over to using KDFONTOP exactly _because_
of this bug (ahem.. 12 years ago ;-).

Reported-by: Minh Yuan <yuanmingbuaa@gmail.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Jiri Slaby <jirislaby@kernel.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

(cherry picked from commit c2313d7818b979f8b3751f052a8db34a7ed26780 linux-stable/linux-5.4.y)
CVE-2020-25668
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---
 drivers/tty/vt/vt_ioctl.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

Comments

Thadeu Lima de Souza Cascardo Feb. 23, 2021, 3:38 p.m. UTC | #1 
Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
diff mbox series

Patch

diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index e9ebe1520a56..142f3a5a01fc 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -244,7 +244,7 @@  int vt_waitactive(int n)
 
 
 static inline int 
-do_fontx_ioctl(int cmd, struct consolefontdesc __user *user_cfd, int perm, struct console_font_op *op)
+do_fontx_ioctl(struct vc_data *vc, int cmd, struct consolefontdesc __user *user_cfd, int perm, struct console_font_op *op)
 {
 	struct consolefontdesc cfdarg;
 	int i;
@@ -262,15 +262,16 @@  do_fontx_ioctl(int cmd, struct consolefontdesc __user *user_cfd, int perm, struc
 		op->height = cfdarg.charheight;
 		op->charcount = cfdarg.charcount;
 		op->data = cfdarg.chardata;
-		return con_font_op(vc_cons[fg_console].d, op);
-	case GIO_FONTX: {
+		return con_font_op(vc, op);
+
+	case GIO_FONTX:
 		op->op = KD_FONT_OP_GET;
 		op->flags = KD_FONT_FLAG_OLD;
 		op->width = 8;
 		op->height = cfdarg.charheight;
 		op->charcount = cfdarg.charcount;
 		op->data = cfdarg.chardata;
-		i = con_font_op(vc_cons[fg_console].d, op);
+		i = con_font_op(vc, op);
 		if (i)
 			return i;
 		cfdarg.charheight = op->height;
@@ -278,7 +279,6 @@  do_fontx_ioctl(int cmd, struct consolefontdesc __user *user_cfd, int perm, struc
 		if (copy_to_user(user_cfd, &cfdarg, sizeof(struct consolefontdesc)))
 			return -EFAULT;
 		return 0;
-		}
 	}
 	return -EINVAL;
 }
@@ -914,7 +914,7 @@  int vt_ioctl(struct tty_struct *tty,
 		op.height = 0;
 		op.charcount = 256;
 		op.data = up;
-		ret = con_font_op(vc_cons[fg_console].d, &op);
+		ret = con_font_op(vc, &op);
 		break;
 	}
 
@@ -925,7 +925,7 @@  int vt_ioctl(struct tty_struct *tty,
 		op.height = 32;
 		op.charcount = 256;
 		op.data = up;
-		ret = con_font_op(vc_cons[fg_console].d, &op);
+		ret = con_font_op(vc, &op);
 		break;
 	}
 
@@ -942,7 +942,7 @@  int vt_ioctl(struct tty_struct *tty,
 
 	case PIO_FONTX:
 	case GIO_FONTX:
-		ret = do_fontx_ioctl(cmd, up, perm, &op);
+		ret = do_fontx_ioctl(vc, cmd, up, perm, &op);
 		break;
 
 	case PIO_FONTRESET:
@@ -959,11 +959,11 @@  int vt_ioctl(struct tty_struct *tty,
 		{
 		op.op = KD_FONT_OP_SET_DEFAULT;
 		op.data = NULL;
-		ret = con_font_op(vc_cons[fg_console].d, &op);
+		ret = con_font_op(vc, &op);
 		if (ret)
 			break;
 		console_lock();
-		con_set_default_unimap(vc_cons[fg_console].d);
+		con_set_default_unimap(vc);
 		console_unlock();
 		break;
 		}
@@ -1090,8 +1090,9 @@  struct compat_consolefontdesc {
 };
 
 static inline int
-compat_fontx_ioctl(int cmd, struct compat_consolefontdesc __user *user_cfd,
-			 int perm, struct console_font_op *op)
+compat_fontx_ioctl(struct vc_data *vc, int cmd,
+		   struct compat_consolefontdesc __user *user_cfd,
+		   int perm, struct console_font_op *op)
 {
 	struct compat_consolefontdesc cfdarg;
 	int i;
@@ -1109,7 +1110,8 @@  compat_fontx_ioctl(int cmd, struct compat_consolefontdesc __user *user_cfd,
 		op->height = cfdarg.charheight;
 		op->charcount = cfdarg.charcount;
 		op->data = compat_ptr(cfdarg.chardata);
-		return con_font_op(vc_cons[fg_console].d, op);
+		return con_font_op(vc, op);
+
 	case GIO_FONTX:
 		op->op = KD_FONT_OP_GET;
 		op->flags = KD_FONT_FLAG_OLD;
@@ -1117,7 +1119,7 @@  compat_fontx_ioctl(int cmd, struct compat_consolefontdesc __user *user_cfd,
 		op->height = cfdarg.charheight;
 		op->charcount = cfdarg.charcount;
 		op->data = compat_ptr(cfdarg.chardata);
-		i = con_font_op(vc_cons[fg_console].d, op);
+		i = con_font_op(vc, op);
 		if (i)
 			return i;
 		cfdarg.charheight = op->height;
@@ -1207,7 +1209,7 @@  long vt_compat_ioctl(struct tty_struct *tty,
 	 */
 	case PIO_FONTX:
 	case GIO_FONTX:
-		return compat_fontx_ioctl(cmd, up, perm, &op);
+		return compat_fontx_ioctl(vc, cmd, up, perm, &op);
 
 	case KDFONTOP:
 		return compat_kdfontop_ioctl(up, perm, &op, vc);