dma-buf: Move BUG_ON from _add_shared_fence to _add_shared_inplace
Fixes the BUG_ON spuriously triggering under the following circumstances: * reservation_object_reserve_shared is called with shared_count == shared_max - 1, so obj->staged is freed in preparation of an in-place update. * reservation_object_add_shared_fence is called with the first fence, after which shared_count == shared_max. * reservation_object_add_shared_fence is called with a follow-up fence from the same context. In the second reservation_object_add_shared_fence call, the BUG_ON triggers. However, nothing bad would happen in reservation_object_add_shared_inplace, since both fences are from the same context, so they only occupy a single slot. Prevent this by moving the BUG_ON to where an overflow would actually happen (e.g. if a buggy caller didn't call reservation_object_reserve_shared before). v2: * Fix description of breaking scenario (Christian König) * Add bugzilla reference Cc: stable@vger.kernel.org Bugzilla: https://bugs.freedesktop.org/106418 Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> # v1 Reviewed-by: Christian König <christian.koenig@amd.com> # v1 Signed-off-by: Michel Dänzer <michel.daenzer@amd.com> Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org> Link: https://patchwork.freedesktop.org/patch/msgid/20180704151405.10357-1-michel@daenzer.net
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@ -141,6 +141,7 @@ reservation_object_add_shared_inplace(struct reservation_object *obj,
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if (signaled) {
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if (signaled) {
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RCU_INIT_POINTER(fobj->shared[signaled_idx], fence);
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RCU_INIT_POINTER(fobj->shared[signaled_idx], fence);
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} else {
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} else {
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BUG_ON(fobj->shared_count >= fobj->shared_max);
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RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
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RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
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fobj->shared_count++;
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fobj->shared_count++;
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}
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}
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@ -230,10 +231,9 @@ void reservation_object_add_shared_fence(struct reservation_object *obj,
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old = reservation_object_get_list(obj);
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old = reservation_object_get_list(obj);
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obj->staged = NULL;
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obj->staged = NULL;
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if (!fobj) {
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if (!fobj)
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BUG_ON(old->shared_count >= old->shared_max);
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reservation_object_add_shared_inplace(obj, old, fence);
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reservation_object_add_shared_inplace(obj, old, fence);
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} else
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else
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reservation_object_add_shared_replace(obj, old, fobj, fence);
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reservation_object_add_shared_replace(obj, old, fobj, fence);
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}
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}
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EXPORT_SYMBOL(reservation_object_add_shared_fence);
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EXPORT_SYMBOL(reservation_object_add_shared_fence);
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