linux-kernel - [PATCH 4.9 21/74] MIPS: VDSO: Prevent use of smp_processor

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Message-Id: <20190919214806.779501443@linuxfoundation.org>
Date:   Fri, 20 Sep 2019 00:03:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paul Burton <paul.burton@...s.com>,
        Matt Redfearn <matt.redfearn@...s.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>, linux-mips@...ux-mips.org,
        Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 4.9 21/74] MIPS: VDSO: Prevent use of smp_processor_id()

From: Paul Burton <paul.burton@...s.com>

commit 351fdddd366245c0fb4636f32edfb4198c8d6b8c upstream.

VDSO code should not be using smp_processor_id(), since it is executed
in user mode.
Introduce a VDSO-specific path which will cause a compile-time
or link-time error (depending upon support for __compiletime_error) if
the VDSO ever incorrectly attempts to use smp_processor_id().

[Matt Redfearn <matt.redfearn@...tec.com>: Move before change to
smp_processor_id in series]

Signed-off-by: Paul Burton <paul.burton@...s.com>
Signed-off-by: Matt Redfearn <matt.redfearn@...s.com>
Patchwork: https://patchwork.linux-mips.org/patch/17932/
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: James Hogan <jhogan@...nel.org>
Cc: linux-mips@...ux-mips.org
Cc: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/mips/include/asm/smp.h |   12 +++++++++++-
 arch/mips/vdso/Makefile     |    3 ++-
 2 files changed, 13 insertions(+), 2 deletions(-)

--- a/arch/mips/include/asm/smp.h
+++ b/arch/mips/include/asm/smp.h
@@ -25,7 +25,17 @@ extern cpumask_t cpu_sibling_map[];
 extern cpumask_t cpu_core_map[];
 extern cpumask_t cpu_foreign_map[];
 
-#define raw_smp_processor_id() (current_thread_info()->cpu)
+static inline int raw_smp_processor_id(void)
+{
+#if defined(__VDSO__)
+	extern int vdso_smp_processor_id(void)
+		__compiletime_error("VDSO should not call smp_processor_id()");
+	return vdso_smp_processor_id();
+#else
+	return current_thread_info()->cpu;
+#endif
+}
+#define raw_smp_processor_id raw_smp_processor_id
 
 /* Map from cpu id to sequential logical cpu number.  This will only
    not be idempotent when cpus failed to come on-line.	*/
--- a/arch/mips/vdso/Makefile
+++ b/arch/mips/vdso/Makefile
@@ -6,7 +6,8 @@ ccflags-vdso := \
 	$(filter -I%,$(KBUILD_CFLAGS)) \
 	$(filter -E%,$(KBUILD_CFLAGS)) \
 	$(filter -mmicromips,$(KBUILD_CFLAGS)) \
-	$(filter -march=%,$(KBUILD_CFLAGS))
+	$(filter -march=%,$(KBUILD_CFLAGS)) \
+	-D__VDSO__
 cflags-vdso := $(ccflags-vdso) \
 	$(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
 	-O2 -g -fPIC -fno-strict-aliasing -fno-common -fno-builtin -G 0 \