From patchwork Tue Apr 12 06:31:46 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 563210 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 25418C433EF for ; Tue, 12 Apr 2022 09:49:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233655AbiDLJvr (ORCPT ); Tue, 12 Apr 2022 05:51:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43172 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1355125AbiDLH1K (ORCPT ); Tue, 12 Apr 2022 03:27:10 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 263A148332; Tue, 12 Apr 2022 00:07:11 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 831A4B81B4D; Tue, 12 Apr 2022 07:07:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BFC52C385A8; Tue, 12 Apr 2022 07:07:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649747228; bh=sXplmjtci3GWzKPGj7qmndHKq1WQI2fvhmgLsZ33CEY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ya39TrhC7pOQ5dpmI0Ywg74BhsGI+zqKBPjvQh0+8MaElBhMIFRKoTzwDuoerDDoi JeUrkx6Cmc1g8VrL7R4+hpJXxdCEyTq1XmSEqAj5F1gw7I8WTLOxDefkbKBi+S+9CB oRHSoHA/2WN5pcGUDBBPU+ThFJH6QIrWDgX6fPzI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Zimmermann , Sudip Mukherjee , Daniel Vetter , Javier Martinez Canillas , Sudip Mukherjee , Zack Rusin , Hans de Goede , Helge Deller , Sam Ravnborg , Zheyu Ma , Xiyu Yang , Zhen Lei , Matthew Wilcox , Alex Deucher , Tetsuo Handa , Guenter Roeck , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: [PATCH 5.16 249/285] fbdev: Fix unregistering of framebuffers without device Date: Tue, 12 Apr 2022 08:31:46 +0200 Message-Id: <20220412062950.845598901@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220412062943.670770901@linuxfoundation.org> References: <20220412062943.670770901@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org From: Thomas Zimmermann commit 0f525289ff0ddeb380813bd81e0f9bdaaa1c9078 upstream. OF framebuffers do not have an underlying device in the Linux device hierarchy. Do a regular unregister call instead of hot unplugging such a non-existing device. Fixes a NULL dereference. An example error message on ppc64le is shown below. BUG: Kernel NULL pointer dereference on read at 0x00000060 Faulting instruction address: 0xc00000000080dfa4 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries [...] CPU: 2 PID: 139 Comm: systemd-udevd Not tainted 5.17.0-ae085d7f9365 #1 NIP: c00000000080dfa4 LR: c00000000080df9c CTR: c000000000797430 REGS: c000000004132fe0 TRAP: 0300 Not tainted (5.17.0-ae085d7f9365) MSR: 8000000002009033 CR: 28228282 XER: 20000000 CFAR: c00000000000c80c DAR: 0000000000000060 DSISR: 40000000 IRQMASK: 0 GPR00: c00000000080df9c c000000004133280 c00000000169d200 0000000000000029 GPR04: 00000000ffffefff c000000004132f90 c000000004132f88 0000000000000000 GPR08: c0000000015658f8 c0000000015cd200 c0000000014f57d0 0000000048228283 GPR12: 0000000000000000 c00000003fffe300 0000000020000000 0000000000000000 GPR16: 0000000000000000 0000000113fc4a40 0000000000000005 0000000113fcfb80 GPR20: 000001000f7283b0 0000000000000000 c000000000e4a588 c000000000e4a5b0 GPR24: 0000000000000001 00000000000a0000 c008000000db0168 c0000000021f6ec0 GPR28: c0000000016d65a8 c000000004b36460 0000000000000000 c0000000016d64b0 NIP [c00000000080dfa4] do_remove_conflicting_framebuffers+0x184/0x1d0 [c000000004133280] [c00000000080df9c] do_remove_conflicting_framebuffers+0x17c/0x1d0 (unreliable) [c000000004133350] [c00000000080e4d0] remove_conflicting_framebuffers+0x60/0x150 [c0000000041333a0] [c00000000080e6f4] remove_conflicting_pci_framebuffers+0x134/0x1b0 [c000000004133450] [c008000000e70438] drm_aperture_remove_conflicting_pci_framebuffers+0x90/0x100 [drm] [c000000004133490] [c008000000da0ce4] bochs_pci_probe+0x6c/0xa64 [bochs] [...] [c000000004133db0] [c00000000002aaa0] system_call_exception+0x170/0x2d0 [c000000004133e10] [c00000000000c3cc] system_call_common+0xec/0x250 The bug [1] was introduced by commit 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal"). Most firmware framebuffers have an underlying platform device, which can be hot-unplugged before loading the native graphics driver. OF framebuffers do not (yet) have that device. Fix the code by unregistering the framebuffer as before without a hot unplug. Tested with 5.17 on qemu ppc64le emulation. Signed-off-by: Thomas Zimmermann Fixes: 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal") Reported-by: Sudip Mukherjee Reviewed-by: Daniel Vetter Reviewed-by: Javier Martinez Canillas Tested-by: Sudip Mukherjee Cc: Zack Rusin Cc: Javier Martinez Canillas Cc: Hans de Goede Cc: stable@vger.kernel.org # v5.11+ Cc: Helge Deller Cc: Daniel Vetter Cc: Sam Ravnborg Cc: Zheyu Ma Cc: Xiyu Yang Cc: Zhen Lei Cc: Matthew Wilcox Cc: Alex Deucher Cc: Tetsuo Handa Cc: Guenter Roeck Cc: linux-fbdev@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Link: https://lore.kernel.org/all/YkHXO6LGHAN0p1pq@debian/ # [1] Link: https://patchwork.freedesktop.org/patch/msgid/20220404194402.29974-1-tzimmermann@suse.de Signed-off-by: Greg Kroah-Hartman --- drivers/video/fbdev/core/fbmem.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1581,7 +1581,14 @@ static void do_remove_conflicting_frameb * If it's not a platform device, at least print a warning. A * fix would add code to remove the device from the system. */ - if (dev_is_platform(device)) { + if (!device) { + /* TODO: Represent each OF framebuffer as its own + * device in the device hierarchy. For now, offb + * doesn't have such a device, so unregister the + * framebuffer as before without warning. + */ + do_unregister_framebuffer(registered_fb[i]); + } else if (dev_is_platform(device)) { registered_fb[i]->forced_out = true; platform_device_unregister(to_platform_device(device)); } else {