linux-hardening - [PATCH v4 11/17] psci: use function_nocfi for cpu

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Date:   Wed, 31 Mar 2021 14:27:15 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Will Deacon <will@...nel.org>, Jessica Yu <jeyu@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Tejun Heo <tj@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sedat Dilek <sedat.dilek@...il.com>, bpf@...r.kernel.org,
        linux-hardening@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH v4 11/17] psci: use function_nocfi for cpu_resume

With CONFIG_CFI_CLANG, the compiler replaces function pointers with
jump table addresses, which results in __pa_symbol returning the
physical address of the jump table entry. As the jump table contains
an immediate jump to an EL1 virtual address, this typically won't
work as intended. Use function_nocfi to get the actual address of
cpu_resume.

Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
 drivers/firmware/psci/psci.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index f5fc429cae3f..64344e84bd63 100644
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -325,8 +325,9 @@ static int __init psci_features(u32 psci_func_id)
 static int psci_suspend_finisher(unsigned long state)
 {
 	u32 power_state = state;
+	phys_addr_t pa_cpu_resume = __pa_symbol(function_nocfi(cpu_resume));
 
-	return psci_ops.cpu_suspend(power_state, __pa_symbol(cpu_resume));
+	return psci_ops.cpu_suspend(power_state, pa_cpu_resume);
 }
 
 int psci_cpu_suspend_enter(u32 state)
@@ -344,8 +345,10 @@ int psci_cpu_suspend_enter(u32 state)
 
 static int psci_system_suspend(unsigned long unused)
 {
+	phys_addr_t pa_cpu_resume = __pa_symbol(function_nocfi(cpu_resume));
+
 	return invoke_psci_fn(PSCI_FN_NATIVE(1_0, SYSTEM_SUSPEND),
-			      __pa_symbol(cpu_resume), 0, 0);
+			      pa_cpu_resume, 0, 0);
 }
 
 static int psci_system_suspend_enter(suspend_state_t state)
-- 
2.31.0.291.g576ba9dcdaf-goog