| Message ID | 20200220225319.45621-1-jbates@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm/virtio: fix resource id creation race | expand |
On Fri, Feb 21, 2020 at 3:14 AM John Bates <jbates@chromium.org> wrote: > > The previous code was not thread safe and caused > undefined behavior from spurious duplicate resource IDs. > In this patch, an atomic_t is used instead. We no longer > see any duplicate IDs in tests with this change. > > Fixes: 16065fcdd19d ("drm/virtio: do NOT reuse resource ids") > Signed-off-by: John Bates <jbates@chromium.org> Reviewed-by: Chia-I Wu <olvaffe@gmail.com> > --- > drivers/gpu/drm/virtio/virtgpu_object.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c > index 017a9e0fc3bb..890121a45625 100644 > --- a/drivers/gpu/drm/virtio/virtgpu_object.c > +++ b/drivers/gpu/drm/virtio/virtgpu_object.c > @@ -42,8 +42,8 @@ static int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev, > * "f91a9dd35715 Fix unlinking resources from hash > * table." (Feb 2019) fixes the bug. > */ > - static int handle; > - handle++; > + static atomic_t seqno = ATOMIC_INIT(0); > + int handle = atomic_inc_return(&seqno); > *resid = handle + 1; resid 1 is (was) discriminated :D > } else { > int handle = ida_alloc(&vgdev->resource_ida, GFP_KERNEL); > -- > 2.25.0.265.gbab2e86ba0-goog > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel
On Fri, Feb 21, 2020 at 10:37 AM Chia-I Wu <olvaffe@gmail.com> wrote: > On Fri, Feb 21, 2020 at 3:14 AM John Bates <jbates@chromium.org> wrote: > > > > The previous code was not thread safe and caused > > undefined behavior from spurious duplicate resource IDs. > > In this patch, an atomic_t is used instead. We no longer > > see any duplicate IDs in tests with this change. > > > > Fixes: 16065fcdd19d ("drm/virtio: do NOT reuse resource ids") > > Signed-off-by: John Bates <jbates@chromium.org> > Reviewed-by: Chia-I Wu <olvaffe@gmail.com> > > --- > > drivers/gpu/drm/virtio/virtgpu_object.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c > b/drivers/gpu/drm/virtio/virtgpu_object.c > > index 017a9e0fc3bb..890121a45625 100644 > > --- a/drivers/gpu/drm/virtio/virtgpu_object.c > > +++ b/drivers/gpu/drm/virtio/virtgpu_object.c > > @@ -42,8 +42,8 @@ static int virtio_gpu_resource_id_get(struct > virtio_gpu_device *vgdev, > > * "f91a9dd35715 Fix unlinking resources from hash > > * table." (Feb 2019) fixes the bug. > > */ > > - static int handle; > > - handle++; > > + static atomic_t seqno = ATOMIC_INIT(0); > > + int handle = atomic_inc_return(&seqno); > > *resid = handle + 1; > resid 1 is (was) discriminated :D > Yup, noticed that too :) > > > } else { > > int handle = ida_alloc(&vgdev->resource_ida, GFP_KERNEL); > > -- > > 2.25.0.265.gbab2e86ba0-goog > > > > _______________________________________________ > > dri-devel mailing list > > dri-devel@lists.freedesktop.org > > https://lists.freedesktop.org/mailman/listinfo/dri-devel >
On Thu, Feb 20, 2020 at 02:53:19PM -0800, John Bates wrote: > The previous code was not thread safe and caused > undefined behavior from spurious duplicate resource IDs. > In this patch, an atomic_t is used instead. We no longer > see any duplicate IDs in tests with this change. > > Fixes: 16065fcdd19d ("drm/virtio: do NOT reuse resource ids") > Signed-off-by: John Bates <jbates@chromium.org> Pushed to drm-misc-fixes. thanks, Gerd
diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c index 017a9e0fc3bb..890121a45625 100644 --- a/drivers/gpu/drm/virtio/virtgpu_object.c +++ b/drivers/gpu/drm/virtio/virtgpu_object.c @@ -42,8 +42,8 @@ static int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev, * "f91a9dd35715 Fix unlinking resources from hash * table." (Feb 2019) fixes the bug. */ - static int handle; - handle++; + static atomic_t seqno = ATOMIC_INIT(0); + int handle = atomic_inc_return(&seqno); *resid = handle + 1; } else { int handle = ida_alloc(&vgdev->resource_ida, GFP_KERNEL);
The previous code was not thread safe and caused undefined behavior from spurious duplicate resource IDs. In this patch, an atomic_t is used instead. We no longer see any duplicate IDs in tests with this change. Fixes: 16065fcdd19d ("drm/virtio: do NOT reuse resource ids") Signed-off-by: John Bates <jbates@chromium.org> --- drivers/gpu/drm/virtio/virtgpu_object.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)