tick/broadcast: Move per CPU pointer access into the atomic section

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: tick/broadcast: Move per CPU pointer access into the atomic section The recent fix for making the take over of the broadcast timer more reliable retrieves a per CPU pointer in preemptible context. This went unnoticed as compilers hoist the access into the non-preemptible region where the pointer is actually used. But of course it's valid that the compiler keeps it at the place where the code puts it which rightfully triggers: BUG: using smp_processor_id() in preemptible [00000000] code: caller is hotplug_cpu__broadcast_tick_pull+0x1c/0xc0 Move it to the actual usage site which is in a non-preemptible region.

References

• https://git.kernel.org/stable/c/f54abf332a2bc0413cfa8bd6a8511f7aa99faea0
• https://git.kernel.org/stable/c/f91fb47ecacc178a83a77eeebd25cbaec18c01d6
• https://git.kernel.org/stable/c/668c6c4a7e9e9f081c06b70f30104fb7013437ed
• https://git.kernel.org/stable/c/541a900d245536d4809cb1aa322c3fcc2cdb58a6
• https://git.kernel.org/stable/c/7b3ec186ba93e333e9efe7254e7e31c1828e5d2d
• https://git.kernel.org/stable/c/b9d604933d5fd72dd37f24e1dc35f778297d745a
• https://git.kernel.org/stable/c/7dd12f85f150010ef7518201c63fa7e395f5c3e9
• https://git.kernel.org/stable/c/6881e75237a84093d0986f56223db3724619f26e