CVE-2022-48922: NULL Pointer Dereference

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

riscv: fix oops caused by irqsoff latency tracer

The trace_hardirqs_{on,off}() require the caller to setup frame pointer properly. This because these two functions use macro 'CALLER_ADDR1' (aka. __builtin_return_address(1)) to acquire caller info. If the $fp is used for other purpose, the code generated this macro (as below) could trigger memory access fault.

0xffffffff8011510e <+80>: ld a1,-16(s0) 0xffffffff80115112 <+84>: ld s2,-8(a1) # <-- paging fault here

The oops message during booting if compiled with 'irqoff' tracer enabled: [ 0.039615][ T0] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000f8 [ 0.041925][ T0] Oops [#1] [ 0.042063][ T0] Modules linked in: [ 0.042864][ T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.17.0-rc1-00233-g9a20c48d1ed2 #29 [ 0.043568][ T0] Hardware name: riscv-virtio,qemu (DT) [ 0.044343][ T0] epc : trace_hardirqs_on+0x56/0xe2 [ 0.044601][ T0] ra : restore_all+0x12/0x6e [ 0.044721][ T0] epc : ffffffff80126a5c ra : ffffffff80003b94 sp : ffffffff81403db0 [ 0.044801][ T0] gp : ffffffff8163acd8 tp : ffffffff81414880 t0 : 0000000000000020 [ 0.044882][ T0] t1 : 0098968000000000 t2 : 0000000000000000 s0 : ffffffff81403de0 [ 0.044967][ T0] s1 : 0000000000000000 a0 : 0000000000000001 a1 : 0000000000000100 [ 0.045046][ T0] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 [ 0.045124][ T0] a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000054494d45 [ 0.045210][ T0] s2 : ffffffff80003b94 s3 : ffffffff81a8f1b0 s4 : ffffffff80e27b50 [ 0.045289][ T0] s5 : ffffffff81414880 s6 : ffffffff8160fa00 s7 : 00000000800120e8 [ 0.045389][ T0] s8 : 0000000080013100 s9 : 000000000000007f s10: 0000000000000000 [ 0.045474][ T0] s11: 0000000000000000 t3 : 7fffffffffffffff t4 : 0000000000000000 [ 0.045548][ T0] t5 : 0000000000000000 t6 : ffffffff814aa368 [ 0.045620][ T0] status: 0000000200000100 badaddr: 00000000000000f8 cause: 000000000000000d [ 0.046402][ T0] [<ffffffff80003b94>] restore_all+0x12/0x6e

This because the $fp(aka. $s0) register is not used as frame pointer in the assembly entry code.

resume_kernel: REG_L s0, TASK_TI_PREEMPT_COUNT(tp) bnez s0, restore_all REG_L s0, TASK_TI_FLAGS(tp) andi s0, s0, _TIF_NEED_RESCHED beqz s0, restore_all call preempt_schedule_irq j restore_all

To fix above issue, here we add one extra level wrapper for function trace_hardirqs_{on,off}() so they can be safely called by low level entry code.