On Wed, 24 Aug 2016, Josh Poimboeuf wrote:
> There's no reliable way to determine which module tainted the kernel
> with CONFIG_LIVEPATCH. For example, /sys/module/<klp module>/taint
> doesn't report it. Neither does the "mod -t" command in the crash tool.
>
> Make it crystal clear who the guilty party is by converting
> CONFIG_LIVEPATCH to a module taint flag.
>
> This changes the behavior a bit: now the the flag gets set when the
> module is loaded, rather than when it's enabled.
>
> Reviewed-by: Chunyu Hu <chuhu@xxxxxxxxxx>
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> ---
> kernel/livepatch/core.c | 3 ---
> kernel/module.c | 35 ++++++++++++-----------------------
> 2 files changed, 12 insertions(+), 26 deletions(-)
>
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 5fbabe0..af46438 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -545,9 +545,6 @@ static int __klp_enable_patch(struct klp_patch *patch)
> list_prev_entry(patch, list)->state == KLP_DISABLED)
> return -EBUSY;
>
> - pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n");
> - add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
> -
> pr_notice("enabling patch '%s'\n", patch->mod->name);
>
> klp_for_each_object(patch, obj) {
> diff --git a/kernel/module.c b/kernel/module.c
> index 529efae..fd5f95b 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -1149,6 +1149,8 @@ static size_t module_flags_taint(struct module *mod, char *buf)
> buf[l++] = 'C';
> if (mod->taints & (1 << TAINT_UNSIGNED_MODULE))
> buf[l++] = 'E';
> + if (mod->taints & (1 << TAINT_LIVEPATCH))
> + buf[l++] = 'K';
> /*
> * TAINT_FORCED_RMMOD: could be added.
> * TAINT_CPU_OUT_OF_SPEC, TAINT_MACHINE_CHECK, TAINT_BAD_PAGE don't
> @@ -2791,26 +2793,6 @@ static int copy_chunked_from_user(void *dst, const void __user *usrc, unsigned l
> return 0;
> }
>
> -#ifdef CONFIG_LIVEPATCH
> -static int find_livepatch_modinfo(struct module *mod, struct load_info *info)
> -{
> - mod->klp = get_modinfo(info, "livepatch") ? true : false;
> -
> - return 0;
> -}
> -#else /* !CONFIG_LIVEPATCH */
> -static int find_livepatch_modinfo(struct module *mod, struct load_info *info)
> -{
> - if (get_modinfo(info, "livepatch")) {
> - pr_err("%s: module is marked as livepatch module, but livepatch support is disabled",
> - mod->name);
> - return -ENOEXEC;
> - }
> -
> - return 0;
> -}
> -#endif /* CONFIG_LIVEPATCH */
> -
> /* Sets info->hdr and info->len. */
> static int copy_module_from_user(const void __user *umod, unsigned long len,
> struct load_info *info)
> @@ -2969,9 +2951,16 @@ static int check_modinfo(struct module *mod, struct load_info *info, int flags)
> "is unknown, you have been warned.\n", mod->name);
> }
>
> - err = find_livepatch_modinfo(mod, info);
> - if (err)
> - return err;
> + if (get_modinfo(info, "livepatch")) {
> + if (!IS_ENABLED(CONFIG_LIVEPATCH)) {
> + pr_err("%s: module is marked as livepatch module, but livepatch support is disabled\n",
> + mod->name);
> + return -ENOEXEC;
> + }
> + mod->klp = true;
> + pr_warn("%s: loading livepatch module.\n", mod->name);
> + add_taint_module(mod, TAINT_LIVEPATCH, LOCKDEP_STILL_OK);
> + }
The old code set mod->klp to false if get_modinfo(info, "livepatch"))
returned true. I think that we don't have to do it, because struct module
of a module is statically allocated (if I am not mistaken) and hence
mod->klp should be initialized to false. However maybe it'd better to do
it explicitly. What do you think?
Miroslav
>
> /* Set up license info based on the info section */
> set_license(mod, get_modinfo(info, "license"));
> --
> 2.7.4
>
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