From: Kees Cook <keescook@chromium.org>
To: Shuah Khan <skhan@linuxfoundation.org>
Cc: shuah@kernel.org, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v3 02/11] selftests:lib:test_counters: add new test for counters
Date: Fri, 9 Oct 2020 11:02:12 -0700 [thread overview]
Message-ID: <202010091102.9073C41@keescook> (raw)
In-Reply-To: <688424d7ff981d34523cd6794d7ce3c27cfe57b4.1602209970.git.skhan@linuxfoundation.org>
On Fri, Oct 09, 2020 at 09:55:57AM -0600, Shuah Khan wrote:
> Add a new selftest for testing counter_atomic* Counters API. This test
> load test_counters test modules and unloads.
>
> The test module runs tests and prints results in dmesg.
>
> There are a number of atomic_t usages in the kernel where atomic_t api
> is used strictly for counting and not for managing object lifetime. In
> some cases, atomic_t might not even be needed.
>
> The purpose of these counters is to clearly differentiate atomic_t
> counters from atomic_t usages that guard object lifetimes, hence prone
> to overflow and underflow errors. It allows tools that scan for underflow
> and overflow on atomic_t usages to detect overflow and underflows to scan
> just the cases that are prone to errors.
>
> Simple atomic counters api provides interfaces for simple atomic counters
> that just count, and don't guard resource lifetimes. The interfaces are
> built on top of atomic_t api, providing a smaller subset of atomic_t
> interfaces necessary to support simple counters.
>
> Counter wraps around to INT_MIN when it overflows and should not be used
> to guard resource lifetimes, device usage and open counts that control
> state changes, and pm states. Overflowing to INT_MIN is consistent with
> the atomic_t api, which it is built on top of.
>
> Using counter_atomic* to guard lifetimes could lead to use-after free
> when it overflows and undefined behavior when used to manage state
> changes and device usage/open states.
>
> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
next prev parent reply other threads:[~2020-10-09 18:02 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-09 15:55 [PATCH v3 00/11] Introduce Simple atomic counters Shuah Khan
2020-10-09 15:55 ` [PATCH v3 01/11] counters: Introduce counter_atomic* counters Shuah Khan
2020-10-09 18:00 ` Kees Cook
2020-10-09 19:49 ` Peter Zijlstra
2020-10-13 11:27 ` Mauro Carvalho Chehab
2020-10-15 1:11 ` Shuah Khan
2020-10-09 15:55 ` [PATCH v3 02/11] selftests:lib:test_counters: add new test for counters Shuah Khan
2020-10-09 18:02 ` Kees Cook [this message]
2020-10-09 15:55 ` [PATCH v3 03/11] drivers/base: convert deferred_trigger_count and probe_count to counter_atomic32 Shuah Khan
2020-10-09 15:55 ` [PATCH v3 04/11] drivers/base/devcoredump: convert devcd_count " Shuah Khan
2020-10-09 18:02 ` Kees Cook
2020-10-09 19:51 ` Peter Zijlstra
2020-10-09 15:56 ` [PATCH v3 05/11] drivers/acpi: convert seqno counter_atomic32 Shuah Khan
2020-10-09 15:56 ` [PATCH v3 06/11] drivers/acpi/apei: " Shuah Khan
2020-10-09 15:56 ` [PATCH v3 07/11] drivers/android/binder: convert stats, transaction_log to counter_atomic32 Shuah Khan
2020-10-09 15:56 ` [PATCH v3 08/11] drivers/base/test/test_async_driver_probe: convert to use counter_atomic32 Shuah Khan
2020-10-09 15:56 ` [PATCH v3 09/11] drivers/char/ipmi: convert stats " Shuah Khan
2020-10-09 15:56 ` [PATCH v3 10/11] drivers/misc/vmw_vmci: convert num guest devices counter to counter_atomic32 Shuah Khan
2020-10-09 15:56 ` [PATCH v3 11/11] drivers/edac: convert pci counters " Shuah Khan
2020-10-09 18:03 ` [PATCH v3 00/11] Introduce Simple atomic counters Kees Cook
2020-10-09 19:02 ` Shuah Khan
2020-10-09 19:37 ` Peter Zijlstra
2020-10-09 20:45 ` Kees Cook
2020-10-10 11:09 ` Peter Zijlstra
2020-10-14 2:12 ` Shuah Khan
2020-10-14 9:17 ` Peter Zijlstra
2020-10-14 23:31 ` Kees Cook
2020-10-16 10:53 ` Peter Zijlstra
2020-10-16 22:51 ` Kees Cook
2020-11-10 18:49 ` Dan Carpenter
2020-10-16 21:56 ` Shuah Khan
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