summaryrefslogtreecommitdiff
path: root/drivers/video
diff options
context:
space:
mode:
authorJiri Slaby (SUSE) <jirislaby@kernel.org>2024-02-08 14:44:11 +0300
committerDaniel Vetter <daniel.vetter@ffwll.ch>2024-02-26 18:47:02 +0300
commit00d6a284fcf3fad1b7e1b5bc3cd87cbfb60ce03f (patch)
treee35a780623d803c3331d29c99e5d32f298ea2c98 /drivers/video
parent9d3f8a723c7950e56e0b95ab84b572caee29e065 (diff)
downloadlinux-00d6a284fcf3fad1b7e1b5bc3cd87cbfb60ce03f.tar.xz
fbcon: always restore the old font data in fbcon_do_set_font()
Commit a5a923038d70 (fbdev: fbcon: Properly revert changes when vc_resize() failed) started restoring old font data upon failure (of vc_resize()). But it performs so only for user fonts. It means that the "system"/internal fonts are not restored at all. So in result, the very first call to fbcon_do_set_font() performs no restore at all upon failing vc_resize(). This can be reproduced by Syzkaller to crash the system on the next invocation of font_get(). It's rather hard to hit the allocation failure in vc_resize() on the first font_set(), but not impossible. Esp. if fault injection is used to aid the execution/failure. It was demonstrated by Sirius: BUG: unable to handle page fault for address: fffffffffffffff8 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD cb7b067 P4D cb7b067 PUD cb7d067 PMD 0 Oops: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 8007 Comm: poc Not tainted 6.7.0-g9d1694dc91ce #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:fbcon_get_font+0x229/0x800 drivers/video/fbdev/core/fbcon.c:2286 Call Trace: <TASK> con_font_get drivers/tty/vt/vt.c:4558 [inline] con_font_op+0x1fc/0xf20 drivers/tty/vt/vt.c:4673 vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline] vt_ioctl+0x632/0x2ec0 drivers/tty/vt/vt_ioctl.c:752 tty_ioctl+0x6f8/0x1570 drivers/tty/tty_io.c:2803 vfs_ioctl fs/ioctl.c:51 [inline] ... So restore the font data in any case, not only for user fonts. Note the later 'if' is now protected by 'old_userfont' and not 'old_data' as the latter is always set now. (And it is supposed to be non-NULL. Otherwise we would see the bug above again.) Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org> Fixes: a5a923038d70 ("fbdev: fbcon: Properly revert changes when vc_resize() failed") Reported-and-tested-by: Ubisectech Sirius <bugreport@ubisectech.com> Cc: Ubisectech Sirius <bugreport@ubisectech.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Helge Deller <deller@gmx.de> Cc: linux-fbdev@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20240208114411.14604-1-jirislaby@kernel.org
Diffstat (limited to 'drivers/video')
-rw-r--r--drivers/video/fbdev/core/fbcon.c8
1 files changed, 3 insertions, 5 deletions
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 1183e7a871f8..46823c2e2ba1 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -2399,11 +2399,9 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount,
struct fbcon_ops *ops = info->fbcon_par;
struct fbcon_display *p = &fb_display[vc->vc_num];
int resize, ret, old_userfont, old_width, old_height, old_charcount;
- char *old_data = NULL;
+ u8 *old_data = vc->vc_font.data;
resize = (w != vc->vc_font.width) || (h != vc->vc_font.height);
- if (p->userfont)
- old_data = vc->vc_font.data;
vc->vc_font.data = (void *)(p->fontdata = data);
old_userfont = p->userfont;
if ((p->userfont = userfont))
@@ -2437,13 +2435,13 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount,
update_screen(vc);
}
- if (old_data && (--REFCOUNT(old_data) == 0))
+ if (old_userfont && (--REFCOUNT(old_data) == 0))
kfree(old_data - FONT_EXTRA_WORDS * sizeof(int));
return 0;
err_out:
p->fontdata = old_data;
- vc->vc_font.data = (void *)old_data;
+ vc->vc_font.data = old_data;
if (userfont) {
p->userfont = old_userfont;