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From: Sami Tolvanen <samitolvanen@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Will Deacon <will@kernel.org>, Jessica Yu <jeyu@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Tejun Heo <tj@kernel.org>,
	bpf@vger.kernel.org, linux-hardening@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kbuild@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Sami Tolvanen <samitolvanen@google.com>
Subject: [PATCH 06/17] kthread: cfi: disable callback pointer check with modules
Date: Thu, 11 Mar 2021 16:49:08 -0800	[thread overview]
Message-ID: <20210312004919.669614-7-samitolvanen@google.com> (raw)
In-Reply-To: <20210312004919.669614-1-samitolvanen@google.com>

With CONFIG_CFI_CLANG, a callback function passed to
__kthread_queue_delayed_work from a module points to a jump table
entry defined in the module instead of the one used in the core
kernel, which breaks function address equality in this check:

  WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);

Disable the warning when CFI and modules are enabled.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 kernel/kthread.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 1578973c5740..af5fee350586 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -963,7 +963,13 @@ static void __kthread_queue_delayed_work(struct kthread_worker *worker,
 	struct timer_list *timer = &dwork->timer;
 	struct kthread_work *work = &dwork->work;
 
-	WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
+	/*
+	 * With CFI, timer->function can point to a jump table entry in a module,
+	 * which fails the comparison. Disable the warning if CFI and modules are
+	 * both enabled.
+	 */
+	if (!IS_ENABLED(CONFIG_CFI_CLANG) || !IS_ENABLED(CONFIG_MODULES))
+		WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
 
 	/*
 	 * If @delay is 0, queue @dwork->work immediately.  This is for
-- 
2.31.0.rc2.261.g7f71774620-goog


WARNING: multiple messages have this Message-ID (diff)
From: Sami Tolvanen <samitolvanen@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	 Masahiro Yamada <masahiroy@kernel.org>,
	Will Deacon <will@kernel.org>, Jessica Yu <jeyu@kernel.org>,
	 Arnd Bergmann <arnd@arndb.de>, Tejun Heo <tj@kernel.org>,
	bpf@vger.kernel.org,  linux-hardening@vger.kernel.org,
	linux-arch@vger.kernel.org,
	 linux-arm-kernel@lists.infradead.org,
	linux-kbuild@vger.kernel.org,  linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	 Sami Tolvanen <samitolvanen@google.com>
Subject: [PATCH 06/17] kthread: cfi: disable callback pointer check with modules
Date: Thu, 11 Mar 2021 16:49:08 -0800	[thread overview]
Message-ID: <20210312004919.669614-7-samitolvanen@google.com> (raw)
In-Reply-To: <20210312004919.669614-1-samitolvanen@google.com>

With CONFIG_CFI_CLANG, a callback function passed to
__kthread_queue_delayed_work from a module points to a jump table
entry defined in the module instead of the one used in the core
kernel, which breaks function address equality in this check:

  WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);

Disable the warning when CFI and modules are enabled.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 kernel/kthread.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 1578973c5740..af5fee350586 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -963,7 +963,13 @@ static void __kthread_queue_delayed_work(struct kthread_worker *worker,
 	struct timer_list *timer = &dwork->timer;
 	struct kthread_work *work = &dwork->work;
 
-	WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
+	/*
+	 * With CFI, timer->function can point to a jump table entry in a module,
+	 * which fails the comparison. Disable the warning if CFI and modules are
+	 * both enabled.
+	 */
+	if (!IS_ENABLED(CONFIG_CFI_CLANG) || !IS_ENABLED(CONFIG_MODULES))
+		WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
 
 	/*
 	 * If @delay is 0, queue @dwork->work immediately.  This is for
-- 
2.31.0.rc2.261.g7f71774620-goog


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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2021-03-12  0:50 UTC|newest]

Thread overview: 84+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-12  0:49 [PATCH 00/17] Add support for Clang CFI Sami Tolvanen
2021-03-12  0:49 ` Sami Tolvanen
2021-03-12  0:49 ` [PATCH 01/17] add " Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:39   ` Kees Cook
2021-03-12  2:39     ` Kees Cook
2021-03-12  0:49 ` [PATCH 02/17] cfi: add __cficanonical Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:40   ` Kees Cook
2021-03-12  2:40     ` Kees Cook
2021-03-12 20:28   ` Bjorn Helgaas
2021-03-12 20:28     ` Bjorn Helgaas
2021-03-12  0:49 ` [PATCH 03/17] mm: add generic __va_function and __pa_function macros Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:40   ` Kees Cook
2021-03-12  2:40     ` Kees Cook
2021-03-12  0:49 ` [PATCH 04/17] module: cfi: ensure __cfi_check alignment Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:39   ` Kees Cook
2021-03-12  2:39     ` Kees Cook
2021-03-16 20:03     ` Sami Tolvanen
2021-03-16 20:03       ` Sami Tolvanen
2021-03-12  0:49 ` [PATCH 05/17] workqueue: cfi: disable callback pointer check with modules Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:43   ` Kees Cook
2021-03-12  2:43     ` Kees Cook
2021-03-12  0:49 ` Sami Tolvanen [this message]
2021-03-12  0:49   ` [PATCH 06/17] kthread: " Sami Tolvanen
2021-03-12  2:43   ` Kees Cook
2021-03-12  2:43     ` Kees Cook
2021-03-12  6:13   ` Christoph Hellwig
2021-03-12  6:13     ` Christoph Hellwig
2021-03-17 16:05     ` Sami Tolvanen
2021-03-17 16:05       ` Sami Tolvanen
2021-03-12  0:49 ` [PATCH 07/17] kallsyms: cfi: strip hashes from static functions Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:45   ` Kees Cook
2021-03-12  2:45     ` Kees Cook
2021-03-16 20:33     ` Sami Tolvanen
2021-03-16 20:33       ` Sami Tolvanen
2021-03-12  0:49 ` [PATCH 08/17] bpf: disable CFI in dispatcher functions Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:45   ` Kees Cook
2021-03-12  2:45     ` Kees Cook
2021-03-12  0:49 ` [PATCH 09/17] lib/list_sort: fix function type mismatches Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:45   ` Kees Cook
2021-03-12  2:45     ` Kees Cook
2021-03-12  0:49 ` [PATCH 10/17] lkdtm: use __va_function Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:45   ` Kees Cook
2021-03-12  2:45     ` Kees Cook
2021-03-12  0:49 ` [PATCH 11/17] psci: use __pa_function for cpu_resume Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:45   ` Kees Cook
2021-03-12  2:45     ` Kees Cook
2021-03-12  0:49 ` [PATCH 12/17] arm64: implement __va_function Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:46   ` Kees Cook
2021-03-12  2:46     ` Kees Cook
2021-03-12  0:49 ` [PATCH 13/17] arm64: use __pa_function Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:46   ` Kees Cook
2021-03-12  2:46     ` Kees Cook
2021-03-12  0:49 ` [PATCH 14/17] arm64: add __nocfi to functions that jump to a physical address Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:47   ` Kees Cook
2021-03-12  2:47     ` Kees Cook
2021-03-12  0:49 ` [PATCH 15/17] arm64: add __nocfi to __apply_alternatives Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:50   ` Kees Cook
2021-03-12  2:50     ` Kees Cook
2021-03-12  0:49 ` [PATCH 16/17] KVM: arm64: Disable CFI for nVHE Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:50   ` Kees Cook
2021-03-12  2:50     ` Kees Cook
2021-03-12  0:49 ` [PATCH 17/17] arm64: allow CONFIG_CFI_CLANG to be selected Sami Tolvanen
2021-03-12  0:49   ` Sami Tolvanen
2021-03-12  2:51   ` Kees Cook
2021-03-12  2:51     ` Kees Cook
2021-03-16 20:44     ` Sami Tolvanen
2021-03-16 20:44       ` Sami Tolvanen
2021-03-16 23:02       ` Kees Cook
2021-03-16 23:02         ` Kees Cook

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