From: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp
[ Upstream commit ec0972adecb391a8d8650832263a4790f3bfb4df ]
syzbot is reporting OOB read at fbcon_resize() [1], for commit 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access") is by error using registered_fb[con2fb_map[vc->vc_num]]->fbcon_par->p->userfont (which was set to non-zero) instead of fb_display[vc->vc_num].userfont (which remains zero for that display).
We could remove tricky userfont flag [2], for we can determine it by comparing address of the font data and addresses of built-in font data. But since that commit is failing to fix the original OOB read [3], this patch keeps the change minimal in case we decide to revert altogether.
[1] https://syzkaller.appspot.com/bug?id=ebcbbb6576958a496500fee9cf7aa83ea00b592... [2] https://syzkaller.appspot.com/text?tag=Patch&x=14030853900000 [3] https://syzkaller.appspot.com/bug?id=6fba8c186d97cf1011ab17660e633b1cc4e080c...
Reported-by: syzbot syzbot+b38b1ef6edf0c74a8d97@syzkaller.appspotmail.com Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Fixes: 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access") Cc: George Kennedy george.kennedy@oracle.com Link: https://lore.kernel.org/r/f6e3e611-8704-1263-d163-f52c906a4f06@I-love.SAKURA... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/video/fbdev/core/fbcon.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index b36bfe10c712c..09cb46e94f405 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2018,7 +2018,7 @@ static int fbcon_resize(struct vc_data *vc, unsigned int width, struct fb_var_screeninfo var = info->var; int x_diff, y_diff, virt_w, virt_h, virt_fw, virt_fh;
- if (ops->p && ops->p->userfont && FNTSIZE(vc->vc_font.data)) { + if (p->userfont && FNTSIZE(vc->vc_font.data)) { int size; int pitch = PITCH(vc->vc_font.width);