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From: Andrew Morton <akpm@linux-foundation.org>
To: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	stable@vger.kernel.org,
	Elena Reshetova <elena.reshetova@intel.com>,
	x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Potapenko <glider@google.com>,
	Alexander Popov <alex.popov@linux.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Jann Horn <jannh@google.com>,
	kernel-hardening@lists.openwall.com,
	linux-hardening@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, Vlastimil Babka <vbabka@suse.cz>,
	David Hildenbrand <david@redhat.com>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH v5 1/7] mm: Restore init_on_* static branch defaults
Date: Wed, 10 Mar 2021 15:56:02 -0800	[thread overview]
Message-ID: <20210310155602.e005171dbecbc0be442f8aad@linux-foundation.org> (raw)
In-Reply-To: <20210309214301.678739-2-keescook@chromium.org>

On Tue,  9 Mar 2021 13:42:55 -0800 Kees Cook <keescook@chromium.org> wrote:

> Choosing the initial state of static branches changes the assembly layout
> (if the condition is expected to be likely, inline, or unlikely, out of
> line via a jump). The _TRUE/_FALSE defines for CONFIG_INIT_ON_*_DEFAULT_ON
> were accidentally removed. These need to stay so that the CONFIG controls
> the pessimization of the resulting static branch NOP/JMP locations.

Changelog doesn't really explain why anyone would want to apply this
patch.  This is especially important for -stable patches.

IOW, what is the user visible effect of the bug?

WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	stable@vger.kernel.org,
	Elena Reshetova <elena.reshetova@intel.com>,
	x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Potapenko <glider@google.com>,
	Alexander Popov <alex.popov@linux.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Jann Horn <jannh@google.com>,
	kernel-hardening@lists.openwall.com,
	linux-hardening@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, Vlastimil Babka <vbabka@suse.cz>,
	David Hildenbrand <david@redhat.com>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH v5 1/7] mm: Restore init_on_* static branch defaults
Date: Wed, 10 Mar 2021 15:56:02 -0800	[thread overview]
Message-ID: <20210310155602.e005171dbecbc0be442f8aad@linux-foundation.org> (raw)
In-Reply-To: <20210309214301.678739-2-keescook@chromium.org>

On Tue,  9 Mar 2021 13:42:55 -0800 Kees Cook <keescook@chromium.org> wrote:

> Choosing the initial state of static branches changes the assembly layout
> (if the condition is expected to be likely, inline, or unlikely, out of
> line via a jump). The _TRUE/_FALSE defines for CONFIG_INIT_ON_*_DEFAULT_ON
> were accidentally removed. These need to stay so that the CONFIG controls
> the pessimization of the resulting static branch NOP/JMP locations.

Changelog doesn't really explain why anyone would want to apply this
patch.  This is especially important for -stable patches.

IOW, what is the user visible effect of the bug?

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-03-10 23:56 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-09 21:42 [PATCH v5 0/7] Optionally randomize kernel stack offset each syscall Kees Cook
2021-03-09 21:42 ` Kees Cook
2021-03-09 21:42 ` [PATCH v5 1/7] mm: Restore init_on_* static branch defaults Kees Cook
2021-03-09 21:42   ` Kees Cook
2021-03-10 23:56   ` Andrew Morton [this message]
2021-03-10 23:56     ` Andrew Morton
2021-03-15 17:28     ` Kees Cook
2021-03-15 17:28       ` Kees Cook
2021-03-09 21:42 ` [PATCH v5 2/7] jump_label: Provide CONFIG-driven build state defaults Kees Cook
2021-03-09 21:42   ` Kees Cook
2021-03-09 21:42 ` [PATCH v5 3/7] init_on_alloc: Unpessimize default-on builds Kees Cook
2021-03-09 21:42   ` Kees Cook
2021-03-10 12:52   ` Andrey Konovalov
2021-03-10 12:52     ` Andrey Konovalov
2021-03-10 12:52     ` Andrey Konovalov
2021-03-10 21:03     ` Kees Cook
2021-03-10 21:03       ` Kees Cook
2021-03-09 21:42 ` [PATCH v5 4/7] stack: Optionally randomize kernel stack offset each syscall Kees Cook
2021-03-09 21:42   ` Kees Cook
2021-03-09 21:42 ` [PATCH v5 5/7] x86/entry: Enable random_kstack_offset support Kees Cook
2021-03-09 21:42   ` Kees Cook
2021-03-09 21:43 ` [PATCH v5 6/7] arm64: entry: " Kees Cook
2021-03-09 21:43   ` Kees Cook
2021-03-09 21:43 ` [PATCH v5 7/7] lkdtm: Add REPORT_STACK for checking stack offsets Kees Cook
2021-03-09 21:43   ` Kees Cook

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