lib: cpu_rmap: Avoid use after free on rmap->obj array entries

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: lib: cpu_rmap: Avoid use after free on rmap->obj array entries When calling irq_set_affinity_notifier() with NULL at the notify argument, it will cause freeing of the glue pointer in the corresponding array entry but will leave the pointer in the array. A subsequent call to free_irq_cpu_rmap() will try to free this entry again leading to possible use after free. Fix that by setting NULL to the array entry and checking that we have non-zero at the array entry when iterating over the array in free_irq_cpu_rmap(). The current code does not suffer from this since there are no cases where irq_set_affinity_notifier(irq, NULL) (note the NULL passed for the notify arg) is called, followed by a call to free_irq_cpu_rmap() so we don't hit and issue. Subsequent patches in this series excersize this flow, hence the required fix.

References

• https://git.kernel.org/stable/c/981f339d2905b6a92ef59358158b326493aecac5
• https://git.kernel.org/stable/c/d1308bd0b24cb1d78fa2747d5fa3e055cc628a48
• https://git.kernel.org/stable/c/cc2d2b3dbfb0ba57bc027fb7e1121250c50e4000
• https://git.kernel.org/stable/c/f748e15253833b771acbede14ea98f50831ac289
• https://git.kernel.org/stable/c/c6ed54dd90698dc0744d669524cc1c122ded8a16
• https://git.kernel.org/stable/c/c9115f49cf260d24d8b5f2d9a4b63cb31a627bb4
• https://git.kernel.org/stable/c/67bca5f1d644f4e79b694abd8052a177de81c37f
• https://git.kernel.org/stable/c/4e0473f1060aa49621d40a113afde24818101d37