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

Overview

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]

Affected

• Linux >= 349e7a85b25fa6ee82902d9be2cc5f3bec815120 < 761db4ca3a469f2070757acd4e104dff5125ca99
• Linux >= 349e7a85b25fa6ee82902d9be2cc5f3bec815120 < fe2329eff5bee461ebcafadb6ca1df0cbf5945fd
• Linux >= 349e7a85b25fa6ee82902d9be2cc5f3bec815120 < 8b83893d1f6c6061a7d58169ecdf9d5ee9f306ee
• Linux >= 349e7a85b25fa6ee82902d9be2cc5f3bec815120 < 934e9d137d937706004c325fa1474f9e3f1ba10a
• Linux 4.12

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.