[PATCH v2 v3.18-rc4 1/4] drm: prime: Honour O_RDWR during prime-handle-to-fd

Daniel Thompson
2014-11-12T11:39:34Z

Currently DRM_IOCTL_PRIME_HANDLE_TO_FD rejects all flags except
(DRM|O)_CLOEXEC making it hard for the userspace to generate a file
descriptor that can be used by mmap().

It is easy to relax the restriction and allow read/write permissions.
This should be safe because the flags are seldom touched by drm; mostly
they are passed verbatim to dma_buf calls.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
---
drivers/gpu/drm/drm_prime.c | 9 +++------
include/uapi/drm/drm.h | 1 +
2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 78ca30808422..8467b17c8053 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -331,7 +331,7 @@ static const struct dma_buf_ops drm_gem_prime_dmabuf_ops = {
* drm_gem_prime_export - helper library implemention of the export callback
* @dev: drm_device to export from
* @obj: GEM object to export
- * @flags: flags like DRM_CLOEXEC
+ * @flags: flags like DRM_CLOEXEC and DRM_RDWR
*
* This is the implementation of the gem_prime_export functions for GEM drivers
* using the PRIME helpers.
@@ -635,14 +635,11 @@ int drm_prime_handle_to_fd_ioctl(struct drm_device *dev, void *data,
return -ENOSYS;

/* check flags are valid */
- if (args->flags & ~DRM_CLOEXEC)
+ if (args->flags & ~(DRM_CLOEXEC | DRM_RDWR))
return -EINVAL;

- /* we only want to pass DRM_CLOEXEC which is == O_CLOEXEC */
- flags = args->flags & DRM_CLOEXEC;
-
return dev->driver->prime_handle_to_fd(dev, file_priv,
- args->handle, flags, &args->fd);
+ args->handle, args->flags, &args->fd);
}

int drm_prime_fd_to_handle_ioctl(struct drm_device *dev, void *data,
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index b0b855613641..89c2b68ddc51 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -660,6 +660,7 @@ struct drm_set_client_cap {
__u64 value;
};

+#define DRM_RDWR O_RDWR
#define DRM_CLOEXEC O_CLOEXEC
struct drm_prime_handle {
__u32 handle;
--
1.9.3