From 9892242166dcc1321a7618da358070affc820924 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 26 Oct 2020 13:15:23 -0700 Subject: [PATCH 2469/2944] tty: make FONTX ioctl use the tty pointer they were actually passed to #31887426 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 Acked-by: Michael Ellerman Acked-by: Jiri Slaby Cc: Greg KH Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman Fixes: CVE-2020-25668 Signed-off-by: Shile Zhang Acked-by: Caspar Zhang --- drivers/tty/vt/vt_ioctl.c | 32 +++++++++++++++++--------------- 1 file changed, 17 insertions(+), 15 deletions(-) diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c index c648b55..6e6907b 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 @@ int vt_waitactive(int n) 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 @@ int vt_waitactive(int n) if (copy_to_user(user_cfd, &cfdarg, sizeof(struct consolefontdesc))) return -EFAULT; return 0; - } } return -EINVAL; } @@ -923,7 +923,7 @@ 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; } @@ -934,7 +934,7 @@ 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; } @@ -951,7 +951,7 @@ 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: @@ -968,11 +968,11 @@ 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; } @@ -1099,8 +1099,9 @@ 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; @@ -1118,7 +1119,8 @@ struct compat_consolefontdesc { 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; @@ -1126,7 +1128,7 @@ struct compat_consolefontdesc { 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; @@ -1225,7 +1227,7 @@ long vt_compat_ioctl(struct tty_struct *tty, */ case PIO_FONTX: case GIO_FONTX: - ret = compat_fontx_ioctl(cmd, up, perm, &op); + ret = compat_fontx_ioctl(vc, cmd, up, perm, &op); break; case KDFONTOP: -- 1.8.3.1