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 8F8301C8776; Mon, 14 Oct 2024 15:30:45 +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=1728919845; cv=none; b=gywHGXE6TM9yGCAdtxGBd4p74YUq3fr4VY2k7xqNwepwnIVyt84zNendSVL0JRgpG8QHFYG4jQPVBrMmM/Mvjmpf7gyGD+2Anizr4mcBZxYiVprVgncHDkqZIgZ0jMUV0RX3sjdhyjbtoFgMfF76DnFT6reaKnYuqV+2bc1LTdA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728919845; c=relaxed/simple; bh=loNX2LRJxCqFDcID3aeKFRrZZ0niVDCNgIXzZI2jRVg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MV2lu2YkMEqzECKn/4lB/r3xeD6OWiQBbAJLpIN1awTKyq0FIzMPGCC4r2QBQuP34+EulVJsgUJ+tM+7dSSMZr/grnB+dT8tb4xG1UoipESIK49bnkQwmGr4+X8WjppgB/iOJ8nbStsL8Q3SxMXMe+gqsAtNaeXcYKFSiq1X1Oo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=YTBLUX3l; 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="YTBLUX3l" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F370EC4CEC3; Mon, 14 Oct 2024 15:30:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1728919845; bh=loNX2LRJxCqFDcID3aeKFRrZZ0niVDCNgIXzZI2jRVg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YTBLUX3l8KEhx4iXueNq2Y3cPvE2Jn3B2E7VGJVVHiCwZR6NZ0V4a2/LxIVbq65NP YN2dcw1lBVn2XEZs1zga/EK7qVikEsNc7I9rSSEkPJG5XGtHLDFe8JJWigWZF4jOHk B+odhqEqTZ2m0I1k+Hp6IJKoz1HygqNaTRQF7KaY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+3d613ae53c031502687a@syzkaller.appspotmail.com, Qianqiang Liu , Helge Deller , Sasha Levin Subject: [PATCH 6.1 723/798] fbcon: Fix a NULL pointer dereference issue in fbcon_putcs Date: Mon, 14 Oct 2024 16:21:17 +0200 Message-ID: <20241014141246.474707391@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241014141217.941104064@linuxfoundation.org> References: <20241014141217.941104064@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Qianqiang Liu [ Upstream commit 5b97eebcce1b4f3f07a71f635d6aa3af96c236e7 ] syzbot has found a NULL pointer dereference bug in fbcon. Here is the simplified C reproducer: struct param { uint8_t type; struct tiocl_selection ts; }; int main() { struct fb_con2fbmap con2fb; struct param param; int fd = open("/dev/fb1", 0, 0); con2fb.console = 0x19; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb); param.type = 2; param.ts.xs = 0; param.ts.ys = 0; param.ts.xe = 0; param.ts.ye = 0; param.ts.sel_mode = 0; int fd1 = open("/dev/tty1", O_RDWR, 0); ioctl(fd1, TIOCLINUX, ¶m); con2fb.console = 1; con2fb.framebuffer = 0; ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb); return 0; } After calling ioctl(fd1, TIOCLINUX, ¶m), the subsequent ioctl(fd, FBIOPUT_CON2FBMAP, &con2fb) causes the kernel to follow a different execution path: set_con2fb_map -> con2fb_init_display -> fbcon_set_disp -> redraw_screen -> hide_cursor -> clear_selection -> highlight -> invert_screen -> do_update_region -> fbcon_putcs -> ops->putcs Since ops->putcs is a NULL pointer, this leads to a kernel panic. To prevent this, we need to call set_blitting_type() within set_con2fb_map() to properly initialize ops->putcs. Reported-by: syzbot+3d613ae53c031502687a@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3d613ae53c031502687a Tested-by: syzbot+3d613ae53c031502687a@syzkaller.appspotmail.com Signed-off-by: Qianqiang Liu Signed-off-by: Helge Deller Signed-off-by: Sasha Levin --- drivers/video/fbdev/core/fbcon.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 14498a0d13e0b..e6640edec155e 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -847,6 +847,8 @@ static int set_con2fb_map(int unit, int newidx, int user) return err; fbcon_add_cursor_work(info); + } else if (vc) { + set_blitting_type(vc, info); } con2fb_map[unit] = newidx; -- 2.43.0