diff options
author | Jiri Slaby (SUSE) <jirislaby@kernel.org> | 2024-02-08 14:44:11 +0300 |
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committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2024-02-26 18:47:02 +0300 |
commit | 00d6a284fcf3fad1b7e1b5bc3cd87cbfb60ce03f (patch) | |
tree | e35a780623d803c3331d29c99e5d32f298ea2c98 /drivers/video/fbdev | |
parent | 9d3f8a723c7950e56e0b95ab84b572caee29e065 (diff) | |
download | linux-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/fbdev')
-rw-r--r-- | drivers/video/fbdev/core/fbcon.c | 8 |
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; |