linux-kernel - [PATCH 1/2] entry: Fix CONFIG

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Message-Id: <20200725091951.744848-2-mingo@kernel.org>
Date:   Sat, 25 Jul 2020 11:19:50 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>
Subject: [PATCH 1/2] entry: Fix CONFIG_SECCOMP assumption

The __secure_computing() callback only exists on CONFIG_SECCOMP=y,
and on architectures that have CONFIG_HAVE_ARCH_SECCOMP_FILTER.

Instead of complicating the #ifdef within the generic entry code,
make the generic entry code depend on the availability of a modern
seccomp framework. This was implicit in the generic code due to
x86 being a modern seccomp-filter architecture.

Also move the Kconfig entry to after its HAVE_ARCH_SECCOMP_FILTER
dependency and fix minor whitespace damage while at it.

Fixes: 142781e108b1: ("entry: Provide generic syscall entry functionality")
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/Kconfig          | 6 ++++--
 kernel/entry/common.c | 2 ++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 852a527f418f..c2b29cfc4796 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -27,8 +27,6 @@ config HAVE_IMA_KEXEC
 config HOTPLUG_SMT
 	bool
 
-config GENERIC_ENTRY
-       bool
 
 config OPROFILE
 	tristate "OProfile system profiling"
@@ -654,6 +652,10 @@ config HAVE_IRQ_EXIT_ON_IRQ_STACK
 	  This spares a stack switch and improves cache usage on softirq
 	  processing.
 
+config GENERIC_ENTRY
+	bool
+	depends on HAVE_ARCH_SECCOMP_FILTER
+
 config PGTABLE_LEVELS
 	int
 	default 2
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 495f5c051b03..49ed8b47773a 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -53,12 +53,14 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall,
 			return -1L;
 	}
 
+#ifdef CONFIG_SECCOMP
 	/* Do seccomp after ptrace, to catch any tracer changes. */
 	if (ti_work & _TIF_SECCOMP) {
 		ret = __secure_computing(NULL);
 		if (ret == -1L)
 			return ret;
 	}
+#endif
 
 	if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT))
 		trace_sys_enter(regs, syscall);
-- 
2.25.1