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Message-ID: <20200716073010.GB971895@kroah.com>
Date: Thu, 16 Jul 2020 09:30:10 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Kees Cook <keescook@...omium.org>
Cc: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
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Mitchell Blank Jr <mitch@...oth.com>,
kernel-hardening@...ts.openwall.com,
Peter Zijlstra <peterz@...radead.org>,
kgdb-bugreport@...ts.sourceforge.net,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
alsa-devel@...a-project.org, Allen Pais <allen.lkml@...il.com>,
Christian Gromm <christian.gromm@...rochip.com>,
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Harald Freudenberger <freude@...ux.ibm.com>,
Thomas Gleixner <tglx@...utronix.de>,
Jaroslav Kysela <perex@...ex.cz>, Felipe Balbi <balbi@...nel.org>,
Kyungtae Kim <kt0755@...il.com>, netdev@...r.kernel.org,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
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Kevin Curtis <kevin.curtis@...site.co.uk>,
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Jason Wessel <jason.wessel@...driver.com>,
Romain Perier <romain.perier@...il.com>,
Karsten Graul <kgraul@...ux.ibm.com>
Subject: Re: [PATCH 3/3] tasklet: Introduce new initialization API
On Wed, Jul 15, 2020 at 08:08:47PM -0700, Kees Cook wrote:
> From: Romain Perier <romain.perier@...il.com>
>
> Nowadays, modern kernel subsystems that use callbacks pass the data
> structure associated with a given callback as argument to the callback.
> The tasklet subsystem remains one which passes an arbitrary unsigned
> long to the callback function. This has several problems:
>
> - This keeps an extra field for storing the argument in each tasklet
> data structure, it bloats the tasklet_struct structure with a redundant
> .data field
>
> - No type checking can be performed on this argument. Instead of
> using container_of() like other callback subsystems, it forces callbacks
> to do explicit type cast of the unsigned long argument into the required
> object type.
>
> - Buffer overflows can overwrite the .func and the .data field, so
> an attacker can easily overwrite the function and its first argument
> to whatever it wants.
>
> Add a new tasklet initialization API, via DECLARE_TASKLET() and
> tasklet_setup(), which will replace the existing ones.
>
> This work is greatly inspired by the timer_struct conversion series,
> see commit e99e88a9d2b0 ("treewide: setup_timer() -> timer_setup()")
>
> To avoid problems with both -Wcast-function-type (which is enabled in
> the kernel via -Wextra is several subsystems), and with mismatched
> function prototypes when build with Control Flow Integrity enabled,
> this adds the "use_callback" member to let the tasklet caller choose
> which union member to call through. Once all old API uses are removed,
> this and the .data member will be removed as well. (On 64-bit this does
> not grow the struct size as the new member fills the hole after atomic_t,
> which is also "int" sized.)
>
> Signed-off-by: Romain Perier <romain.perier@...il.com>
> Co-developed-by: Allen Pais <allen.lkml@...il.com>
> Signed-off-by: Allen Pais <allen.lkml@...il.com>
> Co-developed-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> include/linux/interrupt.h | 24 +++++++++++++++++++++++-
> kernel/softirq.c | 18 +++++++++++++++++-
> 2 files changed, 40 insertions(+), 2 deletions(-)
Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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