[Crash-utility] Re: [PATCH 2/2] Fix for failing to load kernel module

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On Tue, Jun 11, 2024 at 11:38 AM Tao Liu <ltao@xxxxxxxxxx> wrote:
Hi Lianbo,

I have the patch tested, looks good to me, so ack.


Applied:
https://github.com/crash-utility/crash/commit/a20eb05de3c1cab954d49eb8bb9dc7fe5224caa0

Thanks
Lianbo
 
Thanks,
Tao Liu

On Wed, Jun 5, 2024 at 6:06 PM Lianbo Jiang <lijiang@xxxxxxxxxx> wrote:
>
> In some kernel modules such as libie.ko, the mem[MOD_TEXT].size
> may be zero, currently crash will only check its value to determine
> if the module is valid, otherwise it fails to load kernel module with
> the following warning and error:
>
>   WARNING: invalid kernel module size: 0
>         KERNEL: /lib/modules/6.10.0-rc1+/build/vmlinux
>       DUMPFILE: /proc/kcore
>           CPUS: 64
>           DATE: Wed Jun  5 12:49:02 IDT 2024
>         UPTIME: 5 days, 05:57:21
>   LOAD AVERAGE: 0.28, 0.06, 0.02
>          TASKS: 806
>       NODENAME: xxxx
>        RELEASE: 6.10.0-rc1+
>        VERSION: #1 SMP PREEMPT_DYNAMIC Fri May 31 04:56:59 IDT 2024
>        MACHINE: x86_64  (2100 Mhz)
>         MEMORY: 1.6 GB
>            PID: 203686
>        COMMAND: "crash"
>           TASK: ffff9f9bf66d0000  [THREAD_INFO: ffff9f9bf66d0000]
>            CPU: 52
>          STATE: TASK_RUNNING (ACTIVE)
>
>   crash> mod
>   mod: cannot access vmalloc'd module memory
>   crash>
>
> Lets count the module size to check if the module is valid, that will
> avoid the current failure.
>
> Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
> ---
>  kernel.c | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/kernel.c b/kernel.c
> index 1728b70c1b5c..e0dc23b9b233 100644
> --- a/kernel.c
> +++ b/kernel.c
> @@ -3821,9 +3821,21 @@ module_init(void)
>                 case KALLSYMS_V2:
>                         if (THIS_KERNEL_VERSION >= LINUX(2,6,27)) {
>                                 numksyms = UINT(modbuf + OFFSET(module_num_symtab));
> -                               if (MODULE_MEMORY())
> -                                       /* check mem[MOD_TEXT].size only */
> -                                       size = UINT(modbuf + OFFSET(module_mem) + OFFSET(module_memory_size));
> +                               if (MODULE_MEMORY()) {
> +                                       /*
> +                                        * The mem[MOD_TEXT].size may be zero, lets count
> +                                        * the module size as below.
> +                                       */
> +                                       int t;
> +                                       size = 0;
> +                                       for_each_mod_mem_type(t) {
> +                                               if (t == MOD_INIT_TEXT)
> +                                                       break;
> +                                               size += UINT(modbuf + OFFSET(module_mem) +
> +                                                               SIZE(module_memory) * t +
> +                                                               OFFSET(module_memory_size));
> +                                       }
> +                               }
>                                 else
>                                         size = UINT(modbuf + MODULE_OFFSET2(module_core_size, rx));
>                         } else {
> @@ -3926,7 +3938,7 @@ verify_modules(void)
>
>                  for (i = 0, found = FALSE; i < kt->mods_installed; i++) {
>                          lm = &st->load_modules[i];
> -                       if (!kvtop(NULL, lm->mod_base, &paddr, 0)) {
> +                       if (lm->mod_base && !kvtop(NULL, lm->mod_base, &paddr, 0)) {
>                                 irregularities++;
>                                  break;
>                         }
> --
> 2.45.1
> --
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