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Date: Mon, 30 Sep 2019 15:44:32 -0700
From: Kees Cook <keescook@...omium.org>
To: Romain Perier <romain.perier@...il.com>
Cc: kernel-hardening@...ts.openwall.com
Subject: Re: [PRE-REVIEW PATCH 12/16] tasklet: Pass tasklet_struct pointer as
.data in DECLARE_TASKLET
On Sun, Sep 29, 2019 at 06:30:24PM +0200, Romain Perier wrote:
> Now that all tasklet initializations have been replaced, this updates
> the core of the DECLARE_TASKLET macros by passing the pointer of the
> tasklet structure as .data, so current static tasklets will continue to
> work by deadling with the tasklet_struct pointer in their handler,
typo: dealing
> without have to change the API of the macro. It also updates all
> callbacks of all tasklets statically allocated via DECLARE_TASKLET() for
> extracting the the parent data structure of the tasklet by using
> from_tasklet().
I think this patch needs to be broken up... the users of
DECLARE_TASKLET() shouldn't need to be changed along with
DECLARE_TASKLET() since there are casts protecting the arguments.
> [...]
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index f5332ae2dbeb..949bbaeaff0e 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -598,11 +598,14 @@ struct tasklet_struct
> unsigned long data;
> };
>
> +#define TASKLET_DATA_TYPE unsigned long
> +#define TASKLET_FUNC_TYPE void (*)(TASKLET_DATA_TYPE)
> +
> #define DECLARE_TASKLET(name, func, data) \
> -struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(0), func, data }
> +struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(0), (TASKLET_FUNC_TYPE)func, (TASKLET_DATA_TYPE)&name }
>
> #define DECLARE_TASKLET_DISABLED(name, func, data) \
> -struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(1), func, data }
> +struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(1), (TASKLET_FUNC_TYPE)func, (TASKLET_DATA_TYPE)&name }
>
>
> enum
> @@ -673,9 +676,6 @@ extern void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu);
> extern void tasklet_init(struct tasklet_struct *t,
> void (*func)(unsigned long), unsigned long data);
>
> -#define TASKLET_DATA_TYPE unsigned long
> -#define TASKLET_FUNC_TYPE void (*)(TASKLET_DATA_TYPE)
> -
This patch feels like it should be combined with the first one, and only
make the changes to the macros. (And keep them one place: we shouldn't
have to move them later.)
> #define from_tasklet(var, callback_tasklet, tasklet_fieldname) \
> container_of(callback_tasklet, typeof(*var), tasklet_fieldname)
>
> diff --git a/kernel/backtracetest.c b/kernel/backtracetest.c
> index a2a97fa3071b..b5b9e16f0083 100644
> --- a/kernel/backtracetest.c
> +++ b/kernel/backtracetest.c
> @@ -23,7 +23,7 @@ static void backtrace_test_normal(void)
>
> static DECLARE_COMPLETION(backtrace_work);
>
> -static void backtrace_test_irq_callback(unsigned long data)
> +static void backtrace_test_irq_callback(struct tasklet_struct *unused)
> {
> dump_stack();
> complete(&backtrace_work);
And all these other changes should be separated out in a different pass.
--
Kees Cook
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