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.
Attack Parameters
Impact Assessment
CVSS Vector v3.1