linux-kernel - [PATCH] x86: Add missing might_fault() from copy_{to,from}

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Date:	Mon, 16 Nov 2009 15:42:18 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: [PATCH] x86: Add missing might_fault() from copy_{to,from}_user()

In x86-64, copy_to/from_user() rely on assembly routines that never
call might_fault(), making us missing various lockdep checks.

This doesn't apply to __copy_from,to_user() that explicitly handle
these calls, neither is it a problem in x86-32 where
copy_to,from_user() rely on the "__" prefixed versions that also call
might_fault().

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
 arch/x86/include/asm/uaccess_64.h |   10 +++++++++-
 arch/x86/lib/copy_user_64.S       |    4 ++--
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index 7adebac..46324c6 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -19,7 +19,7 @@ __must_check unsigned long
 copy_user_generic(void *to, const void *from, unsigned len);
 
 __must_check unsigned long
-copy_to_user(void __user *to, const void *from, unsigned len);
+_copy_to_user(void __user *to, const void *from, unsigned len);
 __must_check unsigned long
 _copy_from_user(void *to, const void __user *from, unsigned len);
 __must_check unsigned long
@@ -32,6 +32,7 @@ static inline unsigned long __must_check copy_from_user(void *to,
 	int sz = __compiletime_object_size(to);
 	int ret = -EFAULT;
 
+	might_fault();
 	if (likely(sz == -1 || sz >= n))
 		ret = _copy_from_user(to, from, n);
 #ifdef CONFIG_DEBUG_VM
@@ -41,6 +42,13 @@ static inline unsigned long __must_check copy_from_user(void *to,
 	return ret;
 }
 
+static __always_inline __must_check
+int copy_to_user(void __user *dst, const void *src, unsigned size)
+{
+	might_fault();
+
+	return _copy_to_user(dst, src, size);
+}
 
 static __always_inline __must_check
 int __copy_from_user(void *dst, const void __user *src, unsigned size)
diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index 3936998..cf889d4 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -65,7 +65,7 @@
 	.endm
 
 /* Standard copy_to_user with segment limit checking */
-ENTRY(copy_to_user)
+ENTRY(_copy_to_user)
 	CFI_STARTPROC
 	GET_THREAD_INFO(%rax)
 	movq %rdi,%rcx
@@ -75,7 +75,7 @@ ENTRY(copy_to_user)
 	jae bad_to_user
 	ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
 	CFI_ENDPROC
-ENDPROC(copy_to_user)
+ENDPROC(_copy_to_user)
 
 /* Standard copy_from_user with segment limit checking */
 ENTRY(_copy_from_user)
-- 
1.6.2.3

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