From: Shigeru Yoshida syoshida@redhat.com
commit a5a923038d70d2d4a86cb4e3f32625a5ee6e7e24 upstream.
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=3443d3a1fa6d964dd7310a0cb1696d165a3e07c... [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+ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/video/fbdev/core/fbcon.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-)
--- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2413,15 +2413,21 @@ static int fbcon_do_set_font(struct vc_d struct fb_info *info = registered_fb[con2fb_map[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; @@ -2437,7 +2443,9 @@ static int fbcon_do_set_font(struct vc_d 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); @@ -2447,6 +2455,21 @@ static int fbcon_do_set_font(struct vc_d 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; }
/*