arm64: fix oops in concurrently setting insn_emulation sysctls

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: arm64: fix oops in concurrently setting insn_emulation sysctls emulation_proc_handler() changes table->data for proc_dointvec_minmax 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: | update_insn_emulation_mode+0xc0/0x148 | emulation_proc_handler+0x64/0xb8 | proc_sys_call_handler+0x9c/0xf8 | proc_sys_write+0x18/0x20 | __vfs_write+0x20/0x48 | vfs_write+0xe4/0x1d0 | ksys_write+0x70/0xf8 | __arm64_sys_write+0x20/0x28 | el0_svc_common.constprop.0+0x7c/0x1c0 | el0_svc_handler+0x2c/0xa0 | el0_svc+0x8/0x200 To fix this issue, keep the table->data as &insn->current_mode and use container_of() to retrieve the insn pointer. Another mutex is used to protect against the current_mode update but not for retrieving insn_emulation as table->data is no longer changing.

References

• https://git.kernel.org/stable/c/9d5fec6ba2e4117d196a8259ab54615ffe562460
• https://git.kernel.org/stable/c/b51881b1da57fe9877125dfdd0aac5172958fcfd
• https://git.kernel.org/stable/c/04549063d5701976034d8c2bfda3d3a8cbf0409f
• https://git.kernel.org/stable/c/353b4673d01c512303c45cf2346f630cda73b5c9
• https://git.kernel.org/stable/c/cc69ef95988b9ef2fc730ec452a7441efb90ef5e
• https://git.kernel.org/stable/c/6a2fd114678d7fc1b5a0f8865ae98f1c17787455
• https://git.kernel.org/stable/c/07022e07017ee5540f5559b0aeb916e8383c1e1a
• https://git.kernel.org/stable/c/af483947d472eccb79e42059276c4deed76f99a6