linux-kernel - Re: [RFC PATCH 3/7] static_call: use helper to access non-exported key

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 9 Nov 2021 19:53:05 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jason Baron <jbaron@...mai.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mark Rutland <mark.rutland@....com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [RFC PATCH 3/7] static_call: use helper to access non-exported
 key

On Tue, Nov 09, 2021 at 05:45:45PM +0100, Ard Biesheuvel wrote:
> @@ -196,13 +190,21 @@ extern long __static_call_return0(void);
>  	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name));			\
>  	EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name))
>  
> +#define EXPORT_STATIC_CALL_GETKEY_HELPER(name)				\
> +	struct static_call_key *STATIC_CALL_GETKEY(name)(void) {	\
> +		BUG_ON(!core_kernel_text(				\
> +			(unsigned long)__builtin_return_address(0)));	\
> +		return &STATIC_CALL_KEY(name);				\
> +	}								\
> +	EXPORT_SYMBOL_GPL(STATIC_CALL_GETKEY(name))

So if I were a nevarious module, I would look up the above symbol from
kallsyms (it is exported and easily obtainable) and then simply
read the text to discover the key address and we're in business.