From 4c70ac7639f6af6d7c2d01f0307665a4b9afada7 Mon Sep 17 00:00:00 2001 From: Eric Anholt Date: Mon, 30 Apr 2018 16:59:27 -0700 Subject: [PATCH] drm/vc4: Add a pad field to align drm_vc4_submit_cl to 64 bits. I had originally asked Stefan Schake to drop the pad field from the syncobj changes that just landed, because I couldn't come up with a reason to align to 64 bits. Talking with Dave Airlie about the new v3d driver's submit ioctl, we came up with a reason: sizeof() on 64-bit platforms may align to 64 bits, in which case the userspace will be submitting the aligned size and the final 32 bits won't be zero-padded by the kernel. If userspace doesn't zero-fill, then a future ABI change adding a 32-bit field at the end could potentially cause the kernel to read undefined data from old userspace (our userspace happens to use structure initialization that zero-fills, but as a general rule we try not to rely on that in the kernel). Signed-off-by: Eric Anholt Link: https://patchwork.freedesktop.org/patch/msgid/20180430235927.28712-1-eric@anholt.net Reviewed-by: Stefan Schake --- drivers/gpu/drm/vc4/vc4_gem.c | 5 +++++ include/uapi/drm/vc4_drm.h | 2 ++ 2 files changed, 7 insertions(+) diff --git a/drivers/gpu/drm/vc4/vc4_gem.c b/drivers/gpu/drm/vc4/vc4_gem.c index a4c4be3ac6af..7910b9acedd6 100644 --- a/drivers/gpu/drm/vc4/vc4_gem.c +++ b/drivers/gpu/drm/vc4/vc4_gem.c @@ -1132,6 +1132,11 @@ vc4_submit_cl_ioctl(struct drm_device *dev, void *data, return -EINVAL; } + if (args->pad2 != 0) { + DRM_DEBUG("Invalid pad: 0x%08x\n", args->pad2); + return -EINVAL; + } + exec = kcalloc(1, sizeof(*exec), GFP_KERNEL); if (!exec) { DRM_ERROR("malloc failure on exec struct\n"); diff --git a/include/uapi/drm/vc4_drm.h b/include/uapi/drm/vc4_drm.h index 2be4fe3610b8..2cac6277a1d7 100644 --- a/include/uapi/drm/vc4_drm.h +++ b/include/uapi/drm/vc4_drm.h @@ -193,6 +193,8 @@ struct drm_vc4_submit_cl { * render job. 0 means ignore. */ __u32 out_sync; + + __u32 pad2; }; /** -- 2.30.2