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bh=+ObqllStQrLiiew5Hkt5u4NBs6lXTVMlRH2zc8Gliio=; b=qL2ruM1sBk/onf85WIhI7ihrQ0P2MJBashUYZ90CPnN1PfvQUFd0GSfFjEd0x37Xon8Hmq ksvvTQaRV2WnNTAQ== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 8F6D63EA63; Wed, 3 Dec 2025 16:50:19 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id lwRSIUtqMGkRKAAAD6G6ig (envelope-from ); Wed, 03 Dec 2025 16:50:19 +0000 Message-ID: <347972d0-66f7-4c5c-9244-72150f0081c9@suse.de> Date: Wed, 3 Dec 2025 17:50:18 +0100 Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6.12.y] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup To: Sasha Levin , stable@vger.kernel.org Cc: Javier Martinez Canillas , Alex Deucher , dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-fbdev@vger.kernel.org References: <2025120119-edgy-recycled-bcfe@gregkh> <20251202202312.2505097-1-sashal@kernel.org> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-0.999]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; RCPT_COUNT_SEVEN(0.00)[8]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[msgid.link:url,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.com:url,suse.de:email,suse.de:dkim,suse.de:mid,bootlin.com:url,amd.com:email,lists.freedesktop.org:email]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Action: no action X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spam-Level: X-Rspamd-Queue-Id: D51655BDC3 X-Spam-Flag: NO X-Spam-Score: -4.51 Hi, thank you for providing an updated patch. Am 02.12.25 um 21:23 schrieb Sasha Levin: > From: Thomas Zimmermann > > [ Upstream commit eb76d0f5553575599561010f24c277cc5b31d003 ] > > Protect vga_switcheroo_client_fb_set() with console lock. Avoids OOB > access in fbcon_remap_all(). Without holding the console lock the call > races with switching outputs. > > VGA switcheroo calls fbcon_remap_all() when switching clients. The fbcon > function uses struct fb_info.node, which is set by register_framebuffer(). > As the fb-helper code currently sets up VGA switcheroo before registering > the framebuffer, the value of node is -1 and therefore not a legal value. > For example, fbcon uses the value within set_con2fb_map() [1] as an index > into an array. > > Moving vga_switcheroo_client_fb_set() after register_framebuffer() can > result in VGA switching that does not switch fbcon correctly. > > Therefore move vga_switcheroo_client_fb_set() under fbcon_fb_registered(), > which already holds the console lock. Fbdev calls fbcon_fb_registered() > from within register_framebuffer(). Serializes the helper with VGA > switcheroo's call to fbcon_remap_all(). > > Although vga_switcheroo_client_fb_set() takes an instance of struct fb_info > as parameter, it really only needs the contained fbcon state. Moving the > call to fbcon initialization is therefore cleaner than before. Only amdgpu, > i915, nouveau and radeon support vga_switcheroo. For all other drivers, > this change does nothing. > > Signed-off-by: Thomas Zimmermann > Link: https://elixir.bootlin.com/linux/v6.17/source/drivers/video/fbdev/core/fbcon.c#L2942 # [1] > Fixes: 6a9ee8af344e ("vga_switcheroo: initial implementation (v15)") > Acked-by: Javier Martinez Canillas > Acked-by: Alex Deucher > Cc: dri-devel@lists.freedesktop.org > Cc: nouveau@lists.freedesktop.org > Cc: amd-gfx@lists.freedesktop.org > Cc: linux-fbdev@vger.kernel.org > Cc: # v2.6.34+ > Link: https://patch.msgid.link/20251105161549.98836-1-tzimmermann@suse.de > Signed-off-by: Sasha Levin Reviewed-by: Thomas Zimmermann > --- > drivers/gpu/drm/drm_fb_helper.c | 6 ------ > drivers/gpu/drm/i915/display/intel_fbdev.c | 6 ------ > drivers/gpu/drm/radeon/radeon_fbdev.c | 5 ----- > drivers/video/fbdev/core/fbcon.c | 9 +++++++++ > 4 files changed, 9 insertions(+), 17 deletions(-) > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c > index b15ddbd65e7b5..a8971c4eb9f05 100644 > --- a/drivers/gpu/drm/drm_fb_helper.c > +++ b/drivers/gpu/drm/drm_fb_helper.c > @@ -30,9 +30,7 @@ > #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > > #include > -#include > #include > -#include > > #include > #include > @@ -1637,10 +1635,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper) > > strcpy(fb_helper->fb->comm, "[fbcon]"); > > - /* Set the fb info for vgaswitcheroo clients. Does nothing otherwise. */ > - if (dev_is_pci(dev->dev)) > - vga_switcheroo_client_fb_set(to_pci_dev(dev->dev), fb_helper->info); > - > return 0; > } > > diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c > index 49a1ac4f54919..337cc9fc31b19 100644 > --- a/drivers/gpu/drm/i915/display/intel_fbdev.c > +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c > @@ -589,11 +589,8 @@ static int intel_fbdev_restore_mode(struct drm_i915_private *dev_priv) > static void intel_fbdev_client_unregister(struct drm_client_dev *client) > { > struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client); > - struct drm_device *dev = fb_helper->dev; > - struct pci_dev *pdev = to_pci_dev(dev->dev); > > if (fb_helper->info) { > - vga_switcheroo_client_fb_set(pdev, NULL); > drm_fb_helper_unregister_info(fb_helper); > } else { > drm_fb_helper_unprepare(fb_helper); > @@ -620,7 +617,6 @@ static int intel_fbdev_client_hotplug(struct drm_client_dev *client) > { > struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client); > struct drm_device *dev = client->dev; > - struct pci_dev *pdev = to_pci_dev(dev->dev); > int ret; > > if (dev->fb_helper) > @@ -634,8 +630,6 @@ static int intel_fbdev_client_hotplug(struct drm_client_dev *client) > if (ret) > goto err_drm_fb_helper_fini; > > - vga_switcheroo_client_fb_set(pdev, fb_helper->info); > - > return 0; > > err_drm_fb_helper_fini: > diff --git a/drivers/gpu/drm/radeon/radeon_fbdev.c b/drivers/gpu/drm/radeon/radeon_fbdev.c > index fb70de29545c6..a197ba2f2717b 100644 > --- a/drivers/gpu/drm/radeon/radeon_fbdev.c > +++ b/drivers/gpu/drm/radeon/radeon_fbdev.c > @@ -300,10 +300,8 @@ static void radeon_fbdev_client_unregister(struct drm_client_dev *client) > { > struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client); > struct drm_device *dev = fb_helper->dev; > - struct radeon_device *rdev = dev->dev_private; > > if (fb_helper->info) { > - vga_switcheroo_client_fb_set(rdev->pdev, NULL); > drm_helper_force_disable_all(dev); > drm_fb_helper_unregister_info(fb_helper); > } else { > @@ -325,7 +323,6 @@ static int radeon_fbdev_client_hotplug(struct drm_client_dev *client) > { > struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client); > struct drm_device *dev = client->dev; > - struct radeon_device *rdev = dev->dev_private; > int ret; > > if (dev->fb_helper) > @@ -342,8 +339,6 @@ static int radeon_fbdev_client_hotplug(struct drm_client_dev *client) > if (ret) > goto err_drm_fb_helper_fini; > > - vga_switcheroo_client_fb_set(rdev->pdev, fb_helper->info); > - > return 0; > > err_drm_fb_helper_fini: > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c > index 1fc1e47ae2b49..e681066736dea 100644 > --- a/drivers/video/fbdev/core/fbcon.c > +++ b/drivers/video/fbdev/core/fbcon.c > @@ -65,6 +65,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -77,6 +78,7 @@ > #include > #include /* For counting font checksums */ > #include > +#include > #include > > #include "fbcon.h" > @@ -2894,6 +2896,9 @@ void fbcon_fb_unregistered(struct fb_info *info) > > console_lock(); > > + if (info->device && dev_is_pci(info->device)) > + vga_switcheroo_client_fb_set(to_pci_dev(info->device), NULL); > + > fbcon_registered_fb[info->node] = NULL; > fbcon_num_registered_fb--; > > @@ -3027,6 +3032,10 @@ static int do_fb_registered(struct fb_info *info) > } > } > > + /* Set the fb info for vga_switcheroo clients. Does nothing otherwise. */ > + if (info->device && dev_is_pci(info->device)) > + vga_switcheroo_client_fb_set(to_pci_dev(info->device), info); > + > return ret; > } > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)