bus: fsl-mc: fix double-free on mc_dev

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: bus: fsl-mc: fix double-free on mc_dev The blamed commit tried to simplify how the deallocations are done but, in the process, introduced a double-free on the mc_dev variable. In case the MC device is a DPRC, a new mc_bus is allocated and the mc_dev variable is just a reference to one of its fields. In this circumstance, on the error path only the mc_bus should be freed. This commit introduces back the following checkpatch warning which is a false-positive. WARNING: kfree(NULL) is safe and this check is probably not required + if (mc_bus) + kfree(mc_bus);

References

• https://git.kernel.org/stable/c/12e4431e5078847791936820bd39df9e1ee26d2e
• https://git.kernel.org/stable/c/3135e03a92f6b5259d0a7f25f728e9e7866ede3f
• https://git.kernel.org/stable/c/7002b954c4a8b9965ba0f139812ee4a6f71beac8
• https://git.kernel.org/stable/c/b2057374f326303c86d8423415ab58656eebc695
• https://git.kernel.org/stable/c/4b23c46eb2d88924b93aca647bde9a4b9cf62cf9
• https://git.kernel.org/stable/c/1d5baab39e5b09a76870b345cdee7933871b881f
• https://git.kernel.org/stable/c/873d47114fd5e5a1cad2018843671537cc71ac84
• https://git.kernel.org/stable/c/d694bf8a9acdbd061596f3e7549bc8cb70750a60