From patchwork Thu Feb 8 11:44:11 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiri Slaby X-Patchwork-Id: 13549687 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C3AF41DFCE; Thu, 8 Feb 2024 11:44:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707392655; cv=none; b=LWOuUkfSJFkAGB0vI8kQos0v47tqXaw72mbOm4FjzFa4J1/c6RSwBmdd7shBVx+w+8FknijKIYoRiujkfLHmKYOtOG0Kocbb3Gg8eeR4jUxmSJh8Mq2rfTU+LaCOBSXq91GOF+Ctbf7ZAoRN+i9m8mITSHWplmNahngfHZGpOZM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707392655; c=relaxed/simple; bh=yTjseaYVw0yF5zP6CGXqUmZUSPFs3w8SZduU+tXhSIk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=glz3/WeAaL2fyN0Av1DQEoT+AXYZhKKeG3sI3uPK7tyuk0gAfTY8mu8/Zjrx9F6LYzDlgtrtsSO+Loh1y27+Xet/ceLRKGBpWGG9guVx8+uMuiVBuPAZyU+jMtjJGgPD8FWvVN/U9Zhxwf4MhNLQh9/vfRqARYkR8NmPmH42cvk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jTMkDEc+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jTMkDEc+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AC644C433C7; Thu, 8 Feb 2024 11:44:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1707392655; bh=yTjseaYVw0yF5zP6CGXqUmZUSPFs3w8SZduU+tXhSIk=; h=From:To:Cc:Subject:Date:From; b=jTMkDEc+AVCeQA5FQ+dvJWvaP7Ooj+9838vMpKbAYHqtrgXszANRMAkhPuTWyGAVT 2e9yPGMJHM9foZw40JzjPDDKd7pB0haqtDgMbDihQNWr939v1yabMEaXSaiEaA2ziF kjkBztORC/swU8+kRjv+AMIsF94HLF4KvU9F29Jp0/OyiBELf5C+zOoGM5Nv/uIlaw EhHHmPYTeHn5jKUnd9Kk5Qk54tjPwKMbFjH5LIcoDUgI0dD8w+wGyGgRQQuqI/CemB 4m9neYEUnaRWDQ3gLAdT19t80Jh+K6P+2mYcJ2yhhJ0KCgcHapjUJP15KH/pRio3/6 mRd6E6TQwSJbg== From: "Jiri Slaby (SUSE)" To: daniel@ffwll.ch Cc: linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, "Jiri Slaby (SUSE)" , Ubisectech Sirius , Helge Deller Subject: [PATCH] fbcon: always restore the old font data in fbcon_do_set_font() Date: Thu, 8 Feb 2024 12:44:11 +0100 Message-ID: <20240208114411.14604-1-jirislaby@kernel.org> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Commit a5a923038d70 (fbdev: fbcon: Properly revert changes when vc_resize() failed) started restoring old font data upon failure (of vc_resize()). But it performs so only for user fonts. It means that the "system"/internal fonts are not restored at all. So in result, the very first call to fbcon_do_set_font() performs no restore at all upon failing vc_resize(). This can be reproduced by Syzkaller to crash the system on the next invocation of font_get(). It's rather hard to hit the allocation failure in vc_resize() on the first font_set(), but not impossible. Esp. if fault injection is used to aid the execution/failure. It was demonstrated by Sirius: BUG: unable to handle page fault for address: fffffffffffffff8 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD cb7b067 P4D cb7b067 PUD cb7d067 PMD 0 Oops: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 8007 Comm: poc Not tainted 6.7.0-g9d1694dc91ce #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:fbcon_get_font+0x229/0x800 drivers/video/fbdev/core/fbcon.c:2286 Call Trace: con_font_get drivers/tty/vt/vt.c:4558 [inline] con_font_op+0x1fc/0xf20 drivers/tty/vt/vt.c:4673 vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline] vt_ioctl+0x632/0x2ec0 drivers/tty/vt/vt_ioctl.c:752 tty_ioctl+0x6f8/0x1570 drivers/tty/tty_io.c:2803 vfs_ioctl fs/ioctl.c:51 [inline] ... So restore the font data in any case, not only for user fonts. Note the later 'if' is now protected by 'old_userfont' and not 'old_data' as the latter is always set now. (And it is supposed to be non-NULL. Otherwise we would see the bug above again.) Signed-off-by: Jiri Slaby (SUSE) Fixes: a5a923038d70 ("fbdev: fbcon: Properly revert changes when vc_resize() failed") Cc: Ubisectech Sirius Cc: Daniel Vetter Cc: Helge Deller Cc: linux-fbdev@vger.kernel.org Cc: dri-devel@lists.freedesktop.org --- drivers/video/fbdev/core/fbcon.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 17a9fc80b4e4..98d0e2dbcd2f 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2395,11 +2395,9 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount, struct fbcon_ops *ops = info->fbcon_par; struct fbcon_display *p = &fb_display[vc->vc_num]; int resize, ret, old_userfont, old_width, old_height, old_charcount; - char *old_data = NULL; + u8 *old_data = vc->vc_font.data; 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)) @@ -2433,13 +2431,13 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount, update_screen(vc); } - if (old_data && (--REFCOUNT(old_data) == 0)) + if (old_userfont && (--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; + vc->vc_font.data = old_data; if (userfont) { p->userfont = old_userfont;