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authorDaniel Vetter <daniel.vetter@ffwll.ch>2018-08-22 11:54:04 +0300
committerDaniel Vetter <daniel.vetter@ffwll.ch>2018-09-11 15:11:54 +0300
commitda6c7707caf3736c1cf968606bd97c07e79625d4 (patch)
treea8b9621e30d58b35c3547a17d753962ddbeeecde /drivers/video
parent8d7fc2994f4d1f431e280c9e21a139c18dc435ec (diff)
downloadlinux-da6c7707caf3736c1cf968606bd97c07e79625d4.tar.xz
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
Diffstat (limited to 'drivers/video')
-rw-r--r--drivers/video/fbdev/core/fbmem.c4
1 files changed, 4 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));
}