linux-kernel - [PATCH AUTOSEL 4.19 49/52] x86/hw_breakpoints: Make default case in hw_breakpoint_arch

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Date:   Fri, 29 Mar 2019 20:52:56 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Nathan Chancellor <natechancellor@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        clang-built-linux@...glegroups.com, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.19 49/52] x86/hw_breakpoints: Make default case in hw_breakpoint_arch_parse() return an error

From: Nathan Chancellor <natechancellor@...il.com>

[ Upstream commit e898e69d6b9475bf123f99b3c5d1a67bb7cb2361 ]

When building with -Wsometimes-uninitialized, Clang warns:

arch/x86/kernel/hw_breakpoint.c:355:2: warning: variable 'align' is used
uninitialized whenever switch default is taken
[-Wsometimes-uninitialized]

The default cannot be reached because arch_build_bp_info() initializes
hw->len to one of the specified cases. Nevertheless the warning is valid
and returning -EINVAL makes sure that this cannot be broken by future
modifications.

Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: clang-built-linux@...glegroups.com
Link: https://github.com/ClangBuiltLinux/linux/issues/392
Link: https://lkml.kernel.org/r/20190307212756.4648-1-natechancellor@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kernel/hw_breakpoint.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index 34a5c1715148..2882fe1d2a78 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -357,6 +357,7 @@ int hw_breakpoint_arch_parse(struct perf_event *bp,
 #endif
 	default:
 		WARN_ON_ONCE(1);
+		return -EINVAL;
 	}
 
 	/*
-- 
2.19.1