linux-kernel - Re: [PATCH 2/2] module: Show the last unloaded module's taint flag(s)

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Date:   Tue, 28 Jun 2022 05:54:28 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Aaron Tomlin <atomlin@...hat.com>,
        "mcgrof@...nel.org" <mcgrof@...nel.org>
CC:     "linux-modules@...r.kernel.org" <linux-modules@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] module: Show the last unloaded module's taint flag(s)



Le 27/06/2022 à 18:40, Aaron Tomlin a écrit :
> For diagnostic purposes, this patch, in addition to keeping a record/or
> track of the last known unloaded module, we now will include the
> module's taint flag(s) too e.g: " [last unloaded: fpga_mgr_mod(OE)]"
> 
> Signed-off-by: Aaron Tomlin <atomlin@...hat.com>
> ---
>   kernel/module/main.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index dcb83cf18d84..0ca6fd38b903 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -524,7 +524,12 @@ static struct module_attribute modinfo_##field = {                    \
>   MODINFO_ATTR(version);
>   MODINFO_ATTR(srcversion);
>   
> -static char last_unloaded_module[MODULE_NAME_LEN+1];
> +/*
> + * Maximum number of characters written by module_flags()
> + * without a module's state information.
> + */
> +#define LAST_UNLOADED_MODULE_NAME_LEN (MODULE_NAME_LEN + MODULE_FLAGS_BUF_SIZE - 2 + 1)
> +static char last_unloaded_module[LAST_UNLOADED_MODULE_NAME_LEN];
>   
>   #ifdef CONFIG_MODULE_UNLOAD
>   
> @@ -694,6 +699,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
>   {
>   	struct module *mod;
>   	char name[MODULE_NAME_LEN];
> +	char buf[LAST_UNLOADED_MODULE_NAME_LEN];
>   	int ret, forced = 0;
>   
>   	if (!capable(CAP_SYS_MODULE) || modules_disabled)
> @@ -753,8 +759,8 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
>   
>   	async_synchronize_full();
>   
> -	/* Store the name of the last unloaded module for diagnostic purposes */
>   	strlcpy(last_unloaded_module, mod->name, sizeof(last_unloaded_module));
> +	strcat(last_unloaded_module, module_flags(mod, buf, false));

You replace a bounded string copy by an unbounded strict contat.

Should you use strlcat() instead ?

>   
>   	free_module(mod);
>   	/* someone could wait for the module in add_unformed_module() */