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authorTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>2020-09-11 01:57:06 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-09-16 15:35:51 +0300
commitec0972adecb391a8d8650832263a4790f3bfb4df (patch)
tree3ba74018d69ee85776be32e4843c6e3a33549742
parent3c5a87be170aba8ac40982182f812dcff6ed1ad1 (diff)
downloadlinux-ec0972adecb391a8d8650832263a4790f3bfb4df.tar.xz
fbcon: Fix user font detection test at fbcon_resize().
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=ebcbbb6576958a496500fee9cf7aa83ea00b5920 [2] https://syzkaller.appspot.com/text?tag=Patch&x=14030853900000 [3] https://syzkaller.appspot.com/bug?id=6fba8c186d97cf1011ab17660e633b1cc4e080c9 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.ne.jp Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/video/fbdev/core/fbcon.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 66167830fefd..dae7ae7f225a 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -2203,7 +2203,7 @@ 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);