CVE-2026-72095dma-fence: Make dma_fence_dedup_array() robust against 0-count input

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/7aa8f3dba53422465dbe1be8dbb7240304462bb2
• https://git.kernel.org/stable/c/e2d9a2ea178a5da0b4a6693e8ebca5c7fc4d7051
• https://git.kernel.org/stable/c/77a9298741f8f9e8b963c977f5582ab21c6d3427