On Sat, May 07, 2022 at 04:45:10PM +0800, Chen Zhongjin wrote:
> csdlock_debug is a early_param to enable csd_lock_wait
> feature.
>
> It uses static_branch_enable in early_param which triggers
> a panic on arm64 with config:
> CONFIG_SPARSEMEM=y
> CONFIG_SPARSEMEM_VMEMMAP=n
>
> The log shows:
> Unable to handle kernel NULL pointer dereference at
> virtual address ", '0' <repeats 16 times>, "
> ...
> Call trace:
> __aarch64_insn_write+0x9c/0x18c
> ...
> static_key_enable+0x1c/0x30
> csdlock_debug+0x4c/0x78
> do_early_param+0x9c/0xcc
> parse_args+0x26c/0x3a8
> parse_early_options+0x34/0x40
> parse_early_param+0x80/0xa4
> setup_arch+0x150/0x6c8
> start_kernel+0x8c/0x720
> ...
> Kernel panic - not syncing: Oops: Fatal exception
>
> Call trace inside __aarch64_insn_write:
> __nr_to_section
> __pfn_to_page
> phys_to_page
> patch_map
> __aarch64_insn_write
>
> Here, with CONFIG_SPARSEMEM_VMEMMAP=n, __nr_to_section returns
> NULL and makes the NULL dereference because mem_section is
> initialized in sparse_init after parse_early_param stage.
>
> So, static_branch_enable shouldn't be used inside early_param.
> To avoid this, I changed it to __setup and fixed this.
>
> Reported-by: Chen jingwen <chenjingwen6@xxxxxxxxxx>
> Signed-off-by: Chen Zhongjin <chenzhongjin@xxxxxxxxxx>
> ---
> Change v2 -> v3:
> Add module name in title
>
> Change v1 -> v2:
> Fix return 1 for __setup
> ---
>
> kernel/smp.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 65a630f62363..381eb15cd28f 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -174,9 +174,9 @@ static int __init csdlock_debug(char *str)
> if (val)
> static_branch_enable(&csdlock_debug_enabled);
>
> - return 0;
> + return 1;
> }
> -early_param("csdlock_debug", csdlock_debug);
> +__setup("csdlock_debug=", csdlock_debug);
>
> static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
> static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
> --
> 2.17.1
>
<formletter>
This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.
</formletter>
