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[212.51.149.109]) by smtp.gmail.com with ESMTPSA id m35-v6sm8081645ede.14.2018.09.03.09.48.49 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 03 Sep 2018 09:48:49 -0700 (PDT) Date: Mon, 3 Sep 2018 18:48:47 +0200 From: Daniel Vetter To: DRI Development Cc: Intel Graphics Development , LKML , Daniel Vetter , Bartlomiej Zolnierkiewicz , Kees Cook , linux-fbdev@vger.kernel.org, Daniel Vetter Subject: Re: [PATCH 3/4] fbdev: Add FBINFO_HIDE_SMEM_START flag Message-ID: <20180903164847.GM21634@phenom.ffwll.local> Mail-Followup-To: DRI Development , Intel Graphics Development , LKML , Bartlomiej Zolnierkiewicz , Kees Cook , linux-fbdev@vger.kernel.org, Daniel Vetter References: <20180822085405.10787-1-daniel.vetter@ffwll.ch> <20180822085405.10787-3-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180822085405.10787-3-daniel.vetter@ffwll.ch> X-Operating-System: Linux phenom 4.14.0-3-amd64 User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 22, 2018 at 10:54:04AM +0200, Daniel Vetter wrote: > DRM drivers really, really, really don't want random userspace to > share buffer behind it's back, bypassing the dma-buf buffer sharing > machanism. For that reason we've ruthlessly rejected any IOCTL > exposing the physical address of any graphics buffer. > > Unfortunately fbdev comes with that built-in. We could just set > smem_start to 0, but that means we'd have to hand-roll our own fb_mmap > implementation. For good reasons many drivers do that, but > smem_start/length is still super convenient. > > Hence instead just stop the leak in the ioctl, to keep fb mmap working > as-is. A second patch will set this flag for all drm drivers. > > Cc: Bartlomiej Zolnierkiewicz > Cc: Kees Cook > Cc: Daniel Vetter > Cc: linux-fbdev@vger.kernel.org > Signed-off-by: Daniel Vetter Any comments from the fbdev side on this? -Daniel > --- > drivers/video/fbdev/core/fbmem.c | 4 ++++ > include/linux/fb.h | 7 +++++++ > 2 files changed, 11 insertions(+) > > diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c > index 609438d2465b..549d0f86fcf3 100644 > --- a/drivers/video/fbdev/core/fbmem.c > +++ b/drivers/video/fbdev/core/fbmem.c > @@ -1116,6 +1116,8 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, > if (!lock_fb_info(info)) > return -ENODEV; > fix = info->fix; > + if (info->flags & FBINFO_HIDE_SMEM_START) > + fix.smem_start = 0; > unlock_fb_info(info); > > ret = copy_to_user(argp, &fix, sizeof(fix)) ? -EFAULT : 0; > @@ -1326,6 +1328,8 @@ static int fb_get_fscreeninfo(struct fb_info *info, unsigned int cmd, > if (!lock_fb_info(info)) > return -ENODEV; > fix = info->fix; > + if (info->flags & FBINFO_HIDE_SMEM_START) > + fix.smem_start = 0; > unlock_fb_info(info); > return do_fscreeninfo_to_user(&fix, compat_ptr(arg)); > } > diff --git a/include/linux/fb.h b/include/linux/fb.h > index fa8c6f9c9c3a..f42b09ca71f8 100644 > --- a/include/linux/fb.h > +++ b/include/linux/fb.h > @@ -456,6 +456,13 @@ struct fb_tile_ops { > * and host endianness. Drivers should not use this flag. > */ > #define FBINFO_BE_MATH 0x100000 > +/* > + * Hide smem_start in the FBIOGET_FSCREENINFO IOCTL. This is used by modern DRM > + * drivers to stop userspace from trying to share buffers behind the kernel's > + * back. Instead dma-buf based buffer sharing should be used. > + */ > +#define FBINFO_HIDE_SMEM_START 0x200000 > + > > struct fb_info { > atomic_t count; > -- > 2.18.0 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Date: Mon, 03 Sep 2018 16:48:47 +0000 Subject: Re: [PATCH 3/4] fbdev: Add FBINFO_HIDE_SMEM_START flag Message-Id: <20180903164847.GM21634@phenom.ffwll.local> List-Id: References: <20180822085405.10787-1-daniel.vetter@ffwll.ch> <20180822085405.10787-3-daniel.vetter@ffwll.ch> In-Reply-To: <20180822085405.10787-3-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: DRI Development Cc: linux-fbdev@vger.kernel.org, Kees Cook , Bartlomiej Zolnierkiewicz , Daniel Vetter , Intel Graphics Development , LKML , Daniel Vetter On Wed, Aug 22, 2018 at 10:54:04AM +0200, Daniel Vetter wrote: > DRM drivers really, really, really don't want random userspace to > share buffer behind it's back, bypassing the dma-buf buffer sharing > machanism. For that reason we've ruthlessly rejected any IOCTL > exposing the physical address of any graphics buffer. > > Unfortunately fbdev comes with that built-in. We could just set > smem_start to 0, but that means we'd have to hand-roll our own fb_mmap > implementation. For good reasons many drivers do that, but > smem_start/length is still super convenient. > > Hence instead just stop the leak in the ioctl, to keep fb mmap working > as-is. A second patch will set this flag for all drm drivers. > > Cc: Bartlomiej Zolnierkiewicz > Cc: Kees Cook > Cc: Daniel Vetter > Cc: linux-fbdev@vger.kernel.org > Signed-off-by: Daniel Vetter Any comments from the fbdev side on this? -Daniel > --- > drivers/video/fbdev/core/fbmem.c | 4 ++++ > include/linux/fb.h | 7 +++++++ > 2 files changed, 11 insertions(+) > > diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c > index 609438d2465b..549d0f86fcf3 100644 > --- a/drivers/video/fbdev/core/fbmem.c > +++ b/drivers/video/fbdev/core/fbmem.c > @@ -1116,6 +1116,8 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, > if (!lock_fb_info(info)) > return -ENODEV; > fix = info->fix; > + if (info->flags & FBINFO_HIDE_SMEM_START) > + fix.smem_start = 0; > unlock_fb_info(info); > > ret = copy_to_user(argp, &fix, sizeof(fix)) ? -EFAULT : 0; > @@ -1326,6 +1328,8 @@ static int fb_get_fscreeninfo(struct fb_info *info, unsigned int cmd, > if (!lock_fb_info(info)) > return -ENODEV; > fix = info->fix; > + if (info->flags & FBINFO_HIDE_SMEM_START) > + fix.smem_start = 0; > unlock_fb_info(info); > return do_fscreeninfo_to_user(&fix, compat_ptr(arg)); > } > diff --git a/include/linux/fb.h b/include/linux/fb.h > index fa8c6f9c9c3a..f42b09ca71f8 100644 > --- a/include/linux/fb.h > +++ b/include/linux/fb.h > @@ -456,6 +456,13 @@ struct fb_tile_ops { > * and host endianness. Drivers should not use this flag. > */ > #define FBINFO_BE_MATH 0x100000 > +/* > + * Hide smem_start in the FBIOGET_FSCREENINFO IOCTL. This is used by modern DRM > + * drivers to stop userspace from trying to share buffers behind the kernel's > + * back. Instead dma-buf based buffer sharing should be used. > + */ > +#define FBINFO_HIDE_SMEM_START 0x200000 > + > > struct fb_info { > atomic_t count; > -- > 2.18.0 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH 3/4] fbdev: Add FBINFO_HIDE_SMEM_START flag Date: Mon, 3 Sep 2018 18:48:47 +0200 Message-ID: <20180903164847.GM21634@phenom.ffwll.local> References: <20180822085405.10787-1-daniel.vetter@ffwll.ch> <20180822085405.10787-3-daniel.vetter@ffwll.ch> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: <20180822085405.10787-3-daniel.vetter@ffwll.ch> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: DRI Development Cc: linux-fbdev@vger.kernel.org, Kees Cook , Bartlomiej Zolnierkiewicz , Daniel 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