Hi, Enze,
On Wed, Jul 19, 2023 at 4:34 PM Enze Li <lienze@xxxxxxxxxx> wrote:
>
> Currently, executing arch_stack_walk can only get the full stack
> information including NMI. This is because the implementation
> of arch_stack_walk is forced to ignore the information passed by the
> regs parameter and use the current stack information instead.
>
> For some detection systems like KFENCE, only partial stack information
> is needed. In particular, the stack frame where the interrupt occurred.
>
> To support KFENCE, this patch modifies the implementation of the
> arch_stack_walk function so that if this function is called with the
> regs argument passed, it retains all the stack information in regs and
> uses it to provide accurate information.
>
> Before the patch applied, I get,
> [ 1.531195 ] ==================================================================
> [ 1.531442 ] BUG: KFENCE: out-of-bounds read in stack_trace_save_regs+0x48/0x6c
> [ 1.531442 ]
> [ 1.531900 ] Out-of-bounds read at 0xffff800012267fff (1B left of kfence-#12):
> [ 1.532046 ] stack_trace_save_regs+0x48/0x6c
> [ 1.532169 ] kfence_report_error+0xa4/0x528
> [ 1.532276 ] kfence_handle_page_fault+0x124/0x270
> [ 1.532388 ] no_context+0x50/0x94
> [ 1.532453 ] do_page_fault+0x1a8/0x36c
> [ 1.532524 ] tlb_do_page_fault_0+0x118/0x1b4
> [ 1.532623 ] test_out_of_bounds_read+0xa0/0x1d8
> [ 1.532745 ] kunit_generic_run_threadfn_adapter+0x1c/0x28
> [ 1.532854 ] kthread+0x124/0x130
> [ 1.532922 ] ret_from_kernel_thread+0xc/0xa4
> <snip>
>
> With this patch applied, I get the correct stack information.
> [ 1.320220 ] ==================================================================
> [ 1.320401 ] BUG: KFENCE: out-of-bounds read in test_out_of_bounds_read+0xa8/0x1d8
> [ 1.320401 ]
> [ 1.320898 ] Out-of-bounds read at 0xffff800012257fff (1B left of kfence-#10):
> [ 1.321134 ] test_out_of_bounds_read+0xa8/0x1d8
> [ 1.321264 ] kunit_generic_run_threadfn_adapter+0x1c/0x28
> [ 1.321392 ] kthread+0x124/0x130
> [ 1.321459 ] ret_from_kernel_thread+0xc/0xa4
> <snip>
>
> Signed-off-by: Enze Li <lienze@xxxxxxxxxx>
> ---
> arch/loongarch/kernel/stacktrace.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/arch/loongarch/kernel/stacktrace.c b/arch/loongarch/kernel/stacktrace.c
> index 2463d2fea21f..21f60811e26f 100644
> --- a/arch/loongarch/kernel/stacktrace.c
> +++ b/arch/loongarch/kernel/stacktrace.c
> @@ -18,16 +18,20 @@ void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
> struct pt_regs dummyregs;
> struct unwind_state state;
>
> - regs = &dummyregs;
> -
> if (task == current) {
> - regs->regs[3] = (unsigned long)__builtin_frame_address(0);
> - regs->csr_era = (unsigned long)__builtin_return_address(0);
> + if (regs)
> + memcpy(&dummyregs, regs, sizeof(*regs));
> + else {
> + dummyregs.regs[3] = (unsigned long)__builtin_frame_address(0);
> + dummyregs.csr_era = (unsigned long)__builtin_return_address(0);
> + }
> } else {
When "task != current", we don't need to handle the "regs != NULL" case?
Huacai
> - regs->regs[3] = thread_saved_fp(task);
> - regs->csr_era = thread_saved_ra(task);
> + dummyregs.regs[3] = thread_saved_fp(task);
> + dummyregs.csr_era = thread_saved_ra(task);
> }
>
> + regs = &dummyregs;
> +
> regs->regs[1] = 0;
> for (unwind_start(&state, task, regs);
> !unwind_done(&state) && !unwind_error(&state); unwind_next_frame(&state)) {
> --
> 2.34.1
>
>
