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fbdev: fbcon: Properly revert changes when vc_resize() failed

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fbcon_do_set_font() calls vc_resize() when font size is changed.
However, if if vc_resize() failed, current implementation doesn't
revert changes for font size, and this causes inconsistent state.

syzbot reported unable to handle page fault due to this issue [1].
syzbot's repro uses fault injection which cause failure for memory
allocation, so vc_resize() failed.

This patch fixes this issue by properly revert changes for font
related date when vc_resize() failed.

Link: https://syzkaller.appspot.com/bug?id=3443d3a1fa6d964dd7310a0cb1696d165a3e07c4 [1]
Reported-by: syzbot+a168dbeaaa7778273c1b@syzkaller.appspotmail.com
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Signed-off-by: Helge Deller <deller@gmx.de>
CC: stable@vger.kernel.org # 5.15+
This commit is contained in:
Shigeru Yoshida 2022-08-19 03:13:36 +09:00 committed by Helge Deller
parent 8d0268585b
commit a5a923038d
1 changed files with 25 additions and 2 deletions
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27
drivers/video/fbdev/core/fbcon.c
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@ -2401,15 +2401,21 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount,
struct fb_info *info = fbcon_info_from_console(vc->vc_num);
struct fbcon_ops *ops = info->fbcon_par;
struct fbcon_display *p = &fb_display[vc->vc_num];
int resize;
int resize, ret, old_userfont, old_width, old_height, old_charcount;
char *old_data = NULL;
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))
REFCOUNT(data)++;
old_width = vc->vc_font.width;
old_height = vc->vc_font.height;
old_charcount = vc->vc_font.charcount;
vc->vc_font.width = w;
vc->vc_font.height = h;
vc->vc_font.charcount = charcount;
@ -2425,7 +2431,9 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount,
rows = FBCON_SWAP(ops->rotate, info->var.yres, info->var.xres);
cols /= w;
rows /= h;
vc_resize(vc, cols, rows);
ret = vc_resize(vc, cols, rows);
if (ret)
goto err_out;
} else if (con_is_visible(vc)
&& vc->vc_mode == KD_TEXT) {
fbcon_clear_margins(vc, 0);
@ -2435,6 +2443,21 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount,
if (old_data && (--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;
if (userfont) {
p->userfont = old_userfont;
REFCOUNT(data)--;
}
vc->vc_font.width = old_width;
vc->vc_font.height = old_height;
vc->vc_font.charcount = old_charcount;
return ret;
}
/*