CVE-2022-50206

In the Linux kernel, the following vulnerability has been resolved:

arm64: fix oops in concurrently setting insn_emulation sysctls

emulationprochandler() changes table->data for procdointvecminmax and can generate the following Oops if called concurrently with itself:

| Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010 | Internal error: Oops: 96000006 [#1] SMP | Call trace: | updateinsnemulationmode+0xc0/0x148 | emulationprochandler+0x64/0xb8 | procsyscallhandler+0x9c/0xf8 | procsyswrite+0x18/0x20 | __vfswrite+0x20/0x48 | vfswrite+0xe4/0x1d0 | ksys_write+0x70/0xf8 | _arm64syswrite+0x20/0x28 | el0svccommon.constprop.0+0x7c/0x1c0 | el0svchandler+0x2c/0xa0 | el0svc+0x8/0x200

To fix this issue, keep the table->data as &insn->currentmode and use containerof() to retrieve the insn pointer. Another mutex is used to protect against the currentmode update but not for retrieving insnemulation as table->data is no longer changing.