[PATCH 5.15 724/731] fbdev: fbcon: release buffer when fbcon_do_set_font() failed

Greg Kroah-Hartman
2022-12-28T16:04:27Z

From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

commit 3c3bfb8586f848317ceba5d777e11204ba3e5758 upstream.

syzbot is reporting memory leak at fbcon_do_set_font() [1], for
commit a5a923038d70 ("fbdev: fbcon: Properly revert changes when
vc_resize() failed") missed that the buffer might be newly allocated
by fbcon_set_font().

Link: https://syzkaller.appspot.com/bug?extid=25bdb7b1703639abd498 [1]
Reported-by: syzbot <syzbot+25bdb7b1703639abd498@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: syzbot <syzbot+25bdb7b1703639abd498@syzkaller.appspotmail.com>
Fixes: a5a923038d70 ("fbdev: fbcon: Properly revert changes when vc_resize() failed")
CC: stable@vger.kernel.org # 5.15+
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/video/fbdev/core/fbcon.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -2462,7 +2462,8 @@ err_out:

if (userfont) {
p->userfont = old_userfont;
- REFCOUNT(data)--;
+ if (--REFCOUNT(data) == 0)
+ kfree(data - FONT_EXTRA_WORDS * sizeof(int));
}

vc->vc_font.width = old_width;