From mboxrd@z Thu Jan 1 00:00:00 1970 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 012E61C6AB; Mon, 4 Mar 2024 21:54:47 +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=1709589288; cv=none; b=lAxLiEirID7eTg9u8SpCOWlA0cQ8x0SAEk8HGZ4idFAn+cyCt+aUf3Tt37XBn2ZQIzFeK4aFafoLI1gQTVCO9N/6fXvA+IVjnGEvQD5a5Ez7ud0dnaGXyuLbtYYPbGuV2lQP1pXNfOtTblLD1uZ9tOrrqgyzOH9d1uTU/qdDTo0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709589288; c=relaxed/simple; bh=iSD8lQrUC2a6huqfUP7TPUMa7hjhEO/fw2MLY3BN+q0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=G+Ui7+cGTrpzcfh4Sib//Bfm+KBrV59Z60+qWbtGPQlHpxo0IDFrX/6SbzN6hosgN6mWZYh801KmCMouuqG6OEvNbcBVPHANZ5csG0i4wJ5wOvoQwIOzcWw+c8wh/pbrLXhH4utLT/f9PXVqe6roE6S9YbPptXgEllw64X+TXL8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=StmttDSk; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="StmttDSk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D5C0C433C7; Mon, 4 Mar 2024 21:54:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1709589287; bh=iSD8lQrUC2a6huqfUP7TPUMa7hjhEO/fw2MLY3BN+q0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=StmttDSkWtfPqp1rjLY5wefMHDM3EAO7I52atZzaLNLCye12WYOkb04upifDt2bUd Ibl6g6kr2oUPiMuN8N7BsDghhzsYkskMaLgrE/83lc8AP8SGYblCfwcg8ACQ42oOlx jJndxkTEPGfdrk88mFlhkUIMTA5dADIoHqjMKhHg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Jiri Slaby (SUSE)" , Ubisectech Sirius , Daniel Vetter , Helge Deller , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Daniel Vetter , Sasha Levin Subject: [PATCH 5.15 44/84] fbcon: always restore the old font data in fbcon_do_set_font() Date: Mon, 4 Mar 2024 21:24:17 +0000 Message-ID: <20240304211543.802938730@linuxfoundation.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240304211542.332206551@linuxfoundation.org> References: <20240304211542.332206551@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiri Slaby (SUSE) [ Upstream commit 00d6a284fcf3fad1b7e1b5bc3cd87cbfb60ce03f ] 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") Reported-and-tested-by: Ubisectech Sirius Cc: Ubisectech Sirius Cc: Daniel Vetter Cc: Helge Deller Cc: linux-fbdev@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20240208114411.14604-1-jirislaby@kernel.org Signed-off-by: Sasha Levin --- 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 b6712655ec1f0..b163b54b868e6 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2409,11 +2409,9 @@ 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)) @@ -2447,13 +2445,13 @@ 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; -- 2.43.0