PCI: endpoint: pci-epf-test: Fix double free that causes kernel to oops

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: PCI: endpoint: pci-epf-test: Fix double free that causes kernel to oops Fix a kernel oops found while testing the stm32_pcie Endpoint driver with handling of PERST# deassertion: During EP initialization, pci_epf_test_alloc_space() allocates all BARs, which are further freed if epc_set_bar() fails (for instance, due to no free inbound window). However, when pci_epc_set_bar() fails, the error path: pci_epc_set_bar() -> pci_epf_free_space() does not clear the previous assignment to epf_test->reg[bar]. Then, if the host reboots, the PERST# deassertion restarts the BAR allocation sequence with the same allocation failure (no free inbound window), creating a double free situation since epf_test->reg[bar] was deallocated and is still non-NULL. Thus, make sure that pci_epf_alloc_space() and pci_epf_free_space() invocations are symmetric, and as such, set epf_test->reg[bar] to NULL when memory is freed. [kwilczynski: commit log]

References

• https://git.kernel.org/stable/c/fe2329eff5bee461ebcafadb6ca1df0cbf5945fd
• https://git.kernel.org/stable/c/8b83893d1f6c6061a7d58169ecdf9d5ee9f306ee
• https://git.kernel.org/stable/c/934e9d137d937706004c325fa1474f9e3f1ba10a