From: Yao Yiqi <[email protected]>
fbcon_rotate_font() caches a rotated copy of the console font in
par->rotated.buf. The buffer is sized from the font's width, height
and charcount, and is rebuilt in fbcon_init(), fbcon_switch() and
fbcon_modechanged(), but not in fbcon_do_set_font().
When the font is changed through KDFONTOP, the new geometry is
installed and vc_resize() redraws before the buffer is rebuilt. The
rotated putcs/cursor ops then index the old buffer with the new cell
size; KASAN reports a slab-out-of-bounds read in soft_cursor().
Rebuild the buffer for the visible console before the redraw, as the
other callers do: select the console's blitting state with
set_blitting_type() (which also uploads the new font's map on
tile-blitting hardware), then rebuild. Background consoles keep
their rebuild at fbcon_switch() time, as the buffer is shared per
framebuffer and must not be updated for a console that is not being
displayed.
Keep the old buffer out of the rebuild so that it can be restored if
vc_resize() fails: clear par->rotated.buf before calling
rotate_font(), which then allocates a fresh buffer. On failure,
err_out puts the old buffer back and re-selects the blitting state
so tile-blitting hardware gets the restored font's map; the font
change fails as a whole, and the error path never runs rotate_font()
again. The retry added by the next patch still covers
fbcon_switch() and fbcon_modechanged(), which cannot roll back.
Unlike the other callers, this one does not fall back to unrotated
rendering on failure: their "par->rotate = FB_ROTATE_UR;
set_blitting_type(vc, info);" pattern is ineffective, because
set_blitting_type() re-derives par->rotate from par->p->con_rotate.
Repairing that fallback is left to separate work.
Fixes: 6cc50e1c5b57 ("[PATCH] fbcon: Console Rotation - Add support to rotate
font bitmap")
Cc: [email protected]
Signed-off-by: Yao Yiqi <[email protected]>
---
Changes in v4:
- Restore the saved rotated buffer on failure instead of re-running
rotate_font(), so that a second allocation failure cannot leave the
console in a third state.
- Keep the old buffer out of the rebuild by allocating a fresh one.
- Abort the font change when the rebuild fails.
- Guard the rotated state with CONFIG_FRAMEBUFFER_CONSOLE_ROTATION.
---
drivers/video/fbdev/core/fbcon.c | 50 ++++++++++++++++++++++++++++++++
1 file changed, 50 insertions(+)
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 01715873ea49..7605e4237ca5 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -2414,6 +2414,11 @@ static int fbcon_do_set_font(struct vc_data *vc, int w,
int h, int charcount,
font_data_t *old_fontdata = p->fontdata;
const u8 *old_data = vc->vc_font.data;
unsigned short old_hi_font_mask = vc->vc_hi_font_mask;
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_ROTATION
+ u8 *saved_rotated_buf = NULL;
+ size_t saved_rotated_bufsize = 0;
+ bool rotated_saved = false;
+#endif
font_data_get(data);
@@ -2432,6 +2437,29 @@ static int fbcon_do_set_font(struct vc_data *vc, int w,
int h, int charcount,
else if (!vc->vc_hi_font_mask && charcount == 512)
set_vc_hi_font(vc, true);
+ /*
+ * Select the console's blitting state and update par->rotated to
+ * match the new font, so that the rendering below does not use a
+ * cache that was built for the old font. Clear the buffer so the
+ * rebuild allocates a fresh one; the old buffer is kept until the
+ * font change can no longer fail.
+ */
+ if (con_is_visible(vc)) {
+ set_blitting_type(vc, info);
+ if (par->bitops->rotate_font) {
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_ROTATION
+ saved_rotated_buf = par->rotated.buf;
+ saved_rotated_bufsize = par->rotated.bufsize;
+ par->rotated.buf = NULL;
+ par->rotated.bufsize = 0;
+ rotated_saved = true;
+#endif
+ ret = par->bitops->rotate_font(info, vc);
+ if (ret)
+ goto err_out;
+ }
+ }
+
if (resize) {
int cols, rows;
@@ -2448,12 +2476,27 @@ static int fbcon_do_set_font(struct vc_data *vc, int w,
int h, int charcount,
update_screen(vc);
}
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_ROTATION
+ if (rotated_saved)
+ kfree(saved_rotated_buf);
+#endif
if (old_fontdata)
font_data_put(old_fontdata);
return 0;
err_out:
+#ifdef CONFIG_FRAMEBUFFER_CONSOLE_ROTATION
+ /*
+ * Drop the buffer built for the new font and restore the saved
+ * one.
+ */
+ if (rotated_saved) {
+ kfree(par->rotated.buf);
+ par->rotated.buf = saved_rotated_buf;
+ par->rotated.bufsize = saved_rotated_bufsize;
+ }
+#endif
p->fontdata = old_fontdata;
vc->vc_font.data = old_data;
vc->vc_font.width = old_width;
@@ -2466,6 +2509,13 @@ static int fbcon_do_set_font(struct vc_data *vc, int w,
int h, int charcount,
else if (!old_hi_font_mask && vc->vc_hi_font_mask)
set_vc_hi_font(vc, false);
+ /*
+ * Re-select the blitting type, which re-uploads the font map on
+ * tile-blitting hardware.
+ */
+ if (con_is_visible(vc))
+ set_blitting_type(vc, info);
+
font_data_put(data);
return ret;
--
2.56.0
