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From: Kees Cook <keescook@chromium.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Kees Cook <keescook@chromium.org>,
	Will Deacon <will@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Boqun Feng <boqun.feng@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	"David S. Miller" <davem@davemloft.net>,
	David Ahern <dsahern@kernel.org>,
	Eric Dumazet <edumazet@google.com>,
	Paolo Abeni <pabeni@redhat.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Uros Bizjak <ubizjak@gmail.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-arch@vger.kernel.org,
	netdev@vger.kernel.org,
	linux-hardening@vger.kernel.org
Subject: [PATCH 1/4] locking/atomic/x86: Silence intentional wrapping addition
Date: Wed, 24 Apr 2024 12:17:34 -0700
Message-Id: <20240424191740.3088894-1-keescook@chromium.org>
In-Reply-To: <20240424191225.work.780-kees@kernel.org>
References: <20240424191225.work.780-kees@kernel.org>
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Use add_wrap() to annotate the addition in atomic_add_return() as
expecting to wrap around.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
Cc: Will Deacon <will@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
 arch/x86/include/asm/atomic.h      | 3 ++-
 arch/x86/include/asm/atomic64_32.h | 2 +-
 arch/x86/include/asm/atomic64_64.h | 2 +-
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h
index 55a55ec04350..a5862a258760 100644
--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -3,6 +3,7 @@
 #define _ASM_X86_ATOMIC_H
 
 #include <linux/compiler.h>
+#include <linux/overflow.h>
 #include <linux/types.h>
 #include <asm/alternative.h>
 #include <asm/cmpxchg.h>
@@ -82,7 +83,7 @@ static __always_inline bool arch_atomic_add_negative(int i, atomic_t *v)
 
 static __always_inline int arch_atomic_add_return(int i, atomic_t *v)
 {
-	return i + xadd(&v->counter, i);
+	return wrapping_add(int, i, xadd(&v->counter, i));
 }
 #define arch_atomic_add_return arch_atomic_add_return
 
diff --git a/arch/x86/include/asm/atomic64_32.h b/arch/x86/include/asm/atomic64_32.h
index 3486d91b8595..608b100e8ffe 100644
--- a/arch/x86/include/asm/atomic64_32.h
+++ b/arch/x86/include/asm/atomic64_32.h
@@ -254,7 +254,7 @@ static __always_inline s64 arch_atomic64_fetch_add(s64 i, atomic64_t *v)
 {
 	s64 old, c = 0;
 
-	while ((old = arch_atomic64_cmpxchg(v, c, c + i)) != c)
+	while ((old = arch_atomic64_cmpxchg(v, c, wrapping_add(s64, c, i))) != c)
 		c = old;
 
 	return old;
diff --git a/arch/x86/include/asm/atomic64_64.h b/arch/x86/include/asm/atomic64_64.h
index 3165c0feedf7..f1dc8aa54b52 100644
--- a/arch/x86/include/asm/atomic64_64.h
+++ b/arch/x86/include/asm/atomic64_64.h
@@ -76,7 +76,7 @@ static __always_inline bool arch_atomic64_add_negative(s64 i, atomic64_t *v)
 
 static __always_inline s64 arch_atomic64_add_return(s64 i, atomic64_t *v)
 {
-	return i + xadd(&v->counter, i);
+	return wrapping_add(s64, i, xadd(&v->counter, i));
 }
 #define arch_atomic64_add_return arch_atomic64_add_return
 
-- 
2.34.1