diff options
| author | Daniel Vetter <daniel.vetter@ffwll.ch> | 2018-08-22 10:54:04 +0200 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2018-09-11 14:11:54 +0200 |
| commit | da6c7707caf3736c1cf968606bd97c07e79625d4 (patch) | |
| tree | a8b9621e30d58b35c3547a17d753962ddbeeecde | |
| parent | 8d7fc2994f4d1f431e280c9e21a139c18dc435ec (diff) | |
| download | linux-rpi-da6c7707caf3736c1cf968606bd97c07e79625d4.tar.gz linux-rpi-da6c7707caf3736c1cf968606bd97c07e79625d4.tar.bz2 linux-rpi-da6c7707caf3736c1cf968606bd97c07e79625d4.zip | |
fbdev: Add FBINFO_HIDE_SMEM_START flag
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.
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: linux-fbdev@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180822085405.10787-3-daniel.vetter@ffwll.ch
| -rw-r--r-- | drivers/video/fbdev/core/fbmem.c | 4 | ||||
| -rw-r--r-- | include/linux/fb.h | 7 |
2 files changed, 11 insertions, 0 deletions
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 0da75c55660d..861bf8081619 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1117,6 +1117,8 @@ 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; @@ -1327,6 +1329,8 @@ 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 b1db5c5eb671..a3cab6dc9b44 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; |