drm/vmwgfx: Fix stale file descriptors on failed usercopy
commit a0f90c8815706981c483a652a6aefca51a5e191c upstream.
A failing usercopy of the fence_rep object will lead to a stale entry in
the file descriptor table as put_unused_fd() won't release it. This
enables userland to refer to a dangling 'file' object through that still
valid file descriptor, leading to all kinds of use-after-free
exploitation scenarios.
Fix this by deferring the call to fd_install() until after the usercopy
has succeeded.
Fixes: c906965dee22 ("drm/vmwgfx: Add export fence to file descriptor support")
Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
index 5eb73de..765f7a6 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
@@ -1002,15 +1002,14 @@
struct vmw_private *dev_priv,
struct vmw_fence_obj **p_fence,
uint32_t *p_handle);
-extern void vmw_execbuf_copy_fence_user(struct vmw_private *dev_priv,
+extern int vmw_execbuf_copy_fence_user(struct vmw_private *dev_priv,
struct vmw_fpriv *vmw_fp,
int ret,
struct drm_vmw_fence_rep __user
*user_fence_rep,
struct vmw_fence_obj *fence,
uint32_t fence_handle,
- int32_t out_fence_fd,
- struct sync_file *sync_file);
+ int32_t out_fence_fd);
bool vmw_cmd_describe(const void *buf, u32 *size, char const **cmd);
/**
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
index ff86d49..e3d2004 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
@@ -3413,17 +3413,17 @@
* Also if copying fails, user-space will be unable to signal the fence object
* so we wait for it immediately, and then unreference the user-space reference.
*/
-void
+int
vmw_execbuf_copy_fence_user(struct vmw_private *dev_priv,
struct vmw_fpriv *vmw_fp, int ret,
struct drm_vmw_fence_rep __user *user_fence_rep,
struct vmw_fence_obj *fence, uint32_t fence_handle,
- int32_t out_fence_fd, struct sync_file *sync_file)
+ int32_t out_fence_fd)
{
struct drm_vmw_fence_rep fence_rep;
if (user_fence_rep == NULL)
- return;
+ return 0;
memset(&fence_rep, 0, sizeof(fence_rep));
@@ -3451,20 +3451,14 @@
* handle.
*/
if (unlikely(ret != 0) && (fence_rep.error == 0)) {
- if (sync_file)
- fput(sync_file->file);
-
- if (fence_rep.fd != -1) {
- put_unused_fd(fence_rep.fd);
- fence_rep.fd = -1;
- }
-
ttm_ref_object_base_unref(vmw_fp->tfile, fence_handle,
TTM_REF_USAGE);
VMW_DEBUG_USER("Fence copy error. Syncing.\n");
(void) vmw_fence_obj_wait(fence, false, false,
VMW_FENCE_WAIT_TIMEOUT);
}
+
+ return ret ? -EFAULT : 0;
}
/**
@@ -3806,16 +3800,23 @@
(void) vmw_fence_obj_wait(fence, false, false,
VMW_FENCE_WAIT_TIMEOUT);
+ }
+ }
+
+ ret = vmw_execbuf_copy_fence_user(dev_priv, vmw_fpriv(file_priv), ret,
+ user_fence_rep, fence, handle, out_fence_fd);
+
+ if (sync_file) {
+ if (ret) {
+ /* usercopy of fence failed, put the file object */
+ fput(sync_file->file);
+ put_unused_fd(out_fence_fd);
} else {
/* Link the fence with the FD created earlier */
fd_install(out_fence_fd, sync_file->file);
}
}
- vmw_execbuf_copy_fence_user(dev_priv, vmw_fpriv(file_priv), ret,
- user_fence_rep, fence, handle, out_fence_fd,
- sync_file);
-
/* Don't unreference when handing fence out */
if (unlikely(out_fence != NULL)) {
*out_fence = fence;
@@ -3833,7 +3834,7 @@
*/
vmw_validation_unref_lists(&val_ctx);
- return 0;
+ return ret;
out_unlock_binding:
mutex_unlock(&dev_priv->binding_mutex);
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
index 178a6cd..874093a 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
@@ -1171,7 +1171,7 @@
}
vmw_execbuf_copy_fence_user(dev_priv, vmw_fp, 0, user_fence_rep, fence,
- handle, -1, NULL);
+ handle, -1);
vmw_fence_obj_unreference(&fence);
return 0;
out_no_create:
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
index 33b1519..0b800c3 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
@@ -2570,7 +2570,7 @@
if (file_priv)
vmw_execbuf_copy_fence_user(dev_priv, vmw_fpriv(file_priv),
ret, user_fence_rep, fence,
- handle, -1, NULL);
+ handle, -1);
if (out_fence)
*out_fence = fence;
else
