dma-fence: Make dma_fence_dedup_array() robust against 0-count input

In the Linux kernel, the following vulnerability has been resolved: dma-fence: Make dma_fence_dedup_array() robust against 0-count input dma_fence_dedup_array() returns 1 when called with num_fences == 0: the for-loop body never executes, j stays at 0, and the final `return ++j` yields 1. This contradicts both the kernel-doc ("Return: Number of unique fences remaining in the array") and the natural expectation that 0 input gives 0 output. The caller __dma_fence_unwrap_merge() bails out via the `if (count == 0 || count == 1)` fast path and so is save. But amdgpu_userq_wait_*() could reach the dedup call with a zero local count and dereference an uninitialized fence slot in the array. Make the contract match the documentation by returning 0 early. This also skips an unnecessary sort() call on an empty array.

Source published

15 Aug 2026 05:52:41 UTC

Source modified

19 Oct 2026 21:19:27 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 3.1 · 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H