In the Linux kernel, the following vulnerability has been resolved:
wifi: brcmfmac: make release_scratchbuffers idempotent
brcmf_pcie_release_scratchbuffers() frees the shared.scratch and
shared.ringupd DMA buffers with dma_free_coherent() but does not clear
the pointers afterwards, unlike the sibling release_ringbuffers() which
NULLs commonrings/flowrings/idxbuf on release.
Both the bus_reset .reset callback (brcmf_pcie_reset) and
brcmf_pcie_remove() call release_scratchbuffers. When reset teardown
has run before removal, remove’s own teardown would call
dma_free_coherent() a second time on the already-freed DMA allocation.
NULL the pointers after free, matching release_ringbuffers(), so a later
release observes that the allocation has already been released. This
patch makes repeated sequential release safe; the reset-work lifetime is
handled separately by the following patch.
This issue was found by an in-house static analysis tool.
