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From: Peilin Ye <yepeilin.cs@gmail.com>
To: Daniel Vetter <daniel.vetter@ffwll.ch>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jirislaby@kernel.org>,
	Thomas Winischhofer <thomas@winischhofer.net>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Nicolas Pitre <nico@fluxnic.net>,
	"Gustavo A . R . Silva" <gustavoars@kernel.org>,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	George Kennedy <george.kennedy@oracle.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Peter Rosin <peda@axentia.se>,
	linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
	dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org,
	Peilin Ye <yepeilin.cs@gmail.com>
Subject: [PATCH v2 2/2] tty/vt: Avoid passing struct console_font_op to con_font_copy()
Date: Mon,  2 Nov 2020 04:37:55 -0500
Message-ID: <72c954371ed9b1d050901b2d498a979017de8a3c.1604306433.git.yepeilin.cs@gmail.com> (raw)
In-Reply-To: <c5563eeea36aae7bd72ea2e985bc610d585ece40.1604306433.git.yepeilin.cs@gmail.com>

con_font_op() is passing an entire `struct console_font_op *` to
con_font_copy(), but con_font_copy() only uses `op->height`. Additionally,
con_font_copy() is silently assigning the unsigned `op->height` to the
signed `con`, then pass it to fbcon_copy_font().

Let con_font_copy() and fbcon_copy_font() pass an unsigned int directly.
Also, add a comment in con_font_op() for less confusion, since ideally
`op->height` should not be used as a console index, as the field name
suggests.

This patch depends on patch "console: Remove dummy con_font_op() callback
implementations".

Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
con_font_set(), con_font_get() and con_font_default() also pass an entire
`console_font_op`.

con_font_get() and con_font_default() actually update the structure (later
copied to userspace), so let them be.

con_font_set() does not update the structure, but it uses all fields of it
except `op`. Avoiding passing `console_font_op` to con_font_set() will
thus make its signature pretty long (6 parameters).

Changes in v2:
  - Remove redundant `con < 0` check in con_font_copy() (kernel test robot
    <lkp@intel.com>)
  - Remove unnecessary range check in fbcon_copy_font(). con_font_copy()
    calls vc_cons_allocated(), which does the check
  - Do not Cc: stable
  - Rewrite the title and commit message accordingly

 drivers/tty/vt/vt.c              | 8 ++++----
 drivers/video/fbdev/core/fbcon.c | 2 +-
 include/linux/console.h          | 2 +-
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 9506a76f3ab6..27821ef97b13 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -4704,9 +4704,8 @@ static int con_font_default(struct vc_data *vc, struct console_font_op *op)
 	return rc;
 }
 
-static int con_font_copy(struct vc_data *vc, struct console_font_op *op)
+static int con_font_copy(struct vc_data *vc, unsigned int con)
 {
-	int con = op->height;
 	int rc;
 
 
@@ -4715,7 +4714,7 @@ static int con_font_copy(struct vc_data *vc, struct console_font_op *op)
 		rc = -EINVAL;
 	else if (!vc->vc_sw->con_font_copy)
 		rc = -ENOSYS;
-	else if (con < 0 || !vc_cons_allocated(con))
+	else if (!vc_cons_allocated(con))
 		rc = -ENOTTY;
 	else if (con == vc->vc_num)	/* nothing to do */
 		rc = 0;
@@ -4735,7 +4734,8 @@ int con_font_op(struct vc_data *vc, struct console_font_op *op)
 	case KD_FONT_OP_SET_DEFAULT:
 		return con_font_default(vc, op);
 	case KD_FONT_OP_COPY:
-		return con_font_copy(vc, op);
+		/* uses op->height as a console index */
+		return con_font_copy(vc, op->height);
 	}
 	return -ENOSYS;
 }
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index cef437817b0d..cb5b5705ea71 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -2451,7 +2451,7 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h,
 	return 0;
 }
 
-static int fbcon_copy_font(struct vc_data *vc, int con)
+static int fbcon_copy_font(struct vc_data *vc, unsigned int con)
 {
 	struct fbcon_display *od = &fb_display[con];
 	struct console_font *f = &vc->vc_font;
diff --git a/include/linux/console.h b/include/linux/console.h
index 4b1e26c4cb42..34855d3f2afd 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -62,7 +62,7 @@ struct consw {
 	int	(*con_font_get)(struct vc_data *vc, struct console_font *font);
 	int	(*con_font_default)(struct vc_data *vc,
 			struct console_font *font, char *name);
-	int	(*con_font_copy)(struct vc_data *vc, int con);
+	int	(*con_font_copy)(struct vc_data *vc, unsigned int con);
 	int     (*con_resize)(struct vc_data *vc, unsigned int width,
 			unsigned int height, unsigned int user);
 	void	(*con_set_palette)(struct vc_data *vc,
-- 
2.25.1


  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-31  7:24 [PATCH 1/2] console: Remove dummy con_font_op() callback implementations Peilin Ye
2020-10-31  7:27 ` [PATCH 2/2] fbcon: Prevent global-out-of-bounds read in fbcon_copy_font() Peilin Ye
2020-11-02  9:36 ` [PATCH v2 1/2] console: Remove dummy con_font_op() callback implementations Peilin Ye
2020-11-02  9:37   ` Peilin Ye [this message]
2020-11-02 10:10     ` [PATCH v2 2/2] tty/vt: Avoid passing struct console_font_op to con_font_copy() Daniel Vetter
2020-11-02 11:12       ` Peilin Ye
2020-11-02 11:30         ` Daniel Vetter
2020-11-02  9:47   ` [PATCH v2 1/2] console: Remove dummy con_font_op() callback implementations Jiri Slaby
2020-11-02 10:13     ` Daniel Vetter
2020-11-02 10:52       ` Peilin Ye
2020-11-06 10:50 ` [PATCH " Greg Kroah-Hartman
2020-11-10 12:49   ` Daniel Vetter
2020-11-10 13:24     ` Peilin Ye
2020-11-10 13:46       ` Daniel Vetter
2020-11-10 13:55         ` Peilin Ye
2020-11-10 14:56     ` Greg Kroah-Hartman

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