[Mesa-dev] [PATCH v2] virgl: Use right key to insert resource to hash.

[Chia-I Wu]

On Mon, Apr 8, 2019 at 11:24 AM Lepton Wu <lepton at chromium.org> wrote:

> On Mon, Apr 8, 2019 at 11:10 AM Chia-I Wu <olvaffe at gmail.com> wrote:
> >
> >
> >
> > On Mon, Apr 8, 2019 at 9:34 AM Lepton Wu <lepton at chromium.org> wrote:
> >>
> >> The old code could use gem name as key when inserting it to bo_handles
> >> hash table while trying to remove it from hash table with bo_handle as
> >> key in virgl_hw_res_destroy and then it fail to remove it from
> bo_handles
> >> hash table. This triggers use after free. Also, we should insert
> resource
> >> to bo_names hash table when handle type is SHARED.
> >>
> >> Signed-off-by: Lepton Wu <lepton at chromium.org>
> >> ---
> >>  .../winsys/virgl/drm/virgl_drm_winsys.c       | 24 +++++++++++++------
> >>  1 file changed, 17 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/src/gallium/winsys/virgl/drm/virgl_drm_winsys.c
> b/src/gallium/winsys/virgl/drm/virgl_drm_winsys.c
> >> index 2cf8b4ba076..af92b6a98fc 100644
> >> --- a/src/gallium/winsys/virgl/drm/virgl_drm_winsys.c
> >> +++ b/src/gallium/winsys/virgl/drm/virgl_drm_winsys.c
> >> @@ -406,6 +406,12 @@ virgl_drm_winsys_resource_create_handle(struct
> virgl_winsys *qws,
> >>        return NULL;
> >>     }
> >>
> >> +   if (whandle->type != WINSYS_HANDLE_TYPE_FD &&
> >> +       whandle->type != WINSYS_HANDLE_TYPE_SHARED) {
> >> +      fprintf(stderr, "Unexpected handle type: %d\n", whandle->type);
> >> +      return NULL;
> >> +   }
> >> +
> >>     mtx_lock(&qdws->bo_handles_mutex);
> >>
> >>     if (whandle->type == WINSYS_HANDLE_TYPE_SHARED) {
> >> @@ -424,13 +430,13 @@ virgl_drm_winsys_resource_create_handle(struct
> virgl_winsys *qws,
> >>           res = NULL;
> >>           goto done;
> >>        }
> >> -   }
> >>
> >> -   res = util_hash_table_get(qdws->bo_handles,
> (void*)(uintptr_t)handle);
> >> -   if (res) {
> >> -      struct virgl_hw_res *r = NULL;
> >> -      virgl_drm_resource_reference(qdws, &r, res);
> >> -      goto done;
> >> +      res = util_hash_table_get(qdws->bo_handles,
> (void*)(uintptr_t)handle);
> >> +      if (res) {
> >> +         struct virgl_hw_res *r = NULL;
> >> +         virgl_drm_resource_reference(qdws, &r, res);
> >> +         goto done;
> >> +      }
> >>     }
> >>
> > You can still run into troubles when asked to import a buffer by both
> its prime fd and its flink name.
> But it seems there is no way to fix it at user space, right? Every
> time we got a flink name for
> the first time, kernel will give a new handle and no way to  reuse any
> res from hash table.
>
Yeah, I think you are right... but that appears to be a kernel bug.  Once
kernel is fixed to return the same handle for the same flink name / prime
fd, we should be ready for that.  Let's see what Dave thinks.

>
> >>     res = CALLOC_STRUCT(virgl_hw_res);
> >> @@ -448,6 +454,8 @@ virgl_drm_winsys_resource_create_handle(struct
> virgl_winsys *qws,
> >>           goto done;
> >>        }
> >>        res->bo_handle = open_arg.handle;
> >> +      res->flinked = true;
> >> +      res->flink = whandle->handle;
> >>     }
> >>     res->name = handle;
> >
> > res->name has no user.  Remove it.
> >
> > It is also less confusing to make sure `handle' means GEM handle at this
> point, by calling either GEM_OPEN or drmPrimeFDToHandle depending on the
> handle type.
> >
> >>
> >> @@ -469,7 +477,9 @@ virgl_drm_winsys_resource_create_handle(struct
> virgl_winsys *qws,
> >>     res->num_cs_references = 0;
> >>     res->fence_fd = -1;
> >>
> >> -   util_hash_table_set(qdws->bo_handles, (void *)(uintptr_t)handle,
> res);
> >> +   util_hash_table_set(qdws->bo_handles, (void
> *)(uintptr_t)res->bo_handle, res);
> >> +   if (whandle->type == WINSYS_HANDLE_TYPE_SHARED)
> >> +      util_hash_table_set(qdws->bo_names, (void
> *)(uintptr_t)res->flink, res);
> >>
> >>  done:
> >>     mtx_unlock(&qdws->bo_handles_mutex);
> >> --
> >> 2.21.0.392.gf8f6787159e-goog
> >>
>
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