[tip:x86/urgent] x86: copy_from_user() should not return -EFAULT

[tip-bot for Heiko Carstens]

Commit-ID:  409d02ef6d74f5e91f5ea4c587b2ee1375f106fc
Gitweb:     http://git.kernel.org/tip/409d02ef6d74f5e91f5ea4c587b2ee1375f106fc
Author:     Heiko Carstens <heiko.carstens@xxxxxxxxxx>
AuthorDate: Tue, 5 Jan 2010 14:19:11 +0100
Committer:  H. Peter Anvin <hpa@xxxxxxxxx>
CommitDate: Tue, 5 Jan 2010 13:45:06 -0800

x86: copy_from_user() should not return -EFAULT

Callers of copy_from_user() expect it to return the number of bytes
it could not copy. In no case it is supposed to return -EFAULT.

In case of a detected buffer overflow just return the requested
length. In addition one could think of a memset that would clear
the size of the target object.

[ hpa: code is not in .32 so not needed for -stable ]

Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Acked-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
LKML-Reference: <20100105131911.GC5480@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>
---
 arch/x86/include/asm/uaccess_32.h |    5 ++---
 arch/x86/include/asm/uaccess_64.h |    5 ++---
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h
index 0c9825e..088d09f 100644
--- a/arch/x86/include/asm/uaccess_32.h
+++ b/arch/x86/include/asm/uaccess_32.h
@@ -205,14 +205,13 @@ static inline unsigned long __must_check copy_from_user(void *to,
 					  unsigned long n)
 {
 	int sz = __compiletime_object_size(to);
-	int ret = -EFAULT;
 
 	if (likely(sz == -1 || sz >= n))
-		ret = _copy_from_user(to, from, n);
+		n = _copy_from_user(to, from, n);
 	else
 		copy_from_user_overflow();
 
-	return ret;
+	return n;
 }
 
 long __must_check strncpy_from_user(char *dst, const char __user *src,
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index 46324c6..535e421 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -30,16 +30,15 @@ static inline unsigned long __must_check copy_from_user(void *to,
 					  unsigned long n)
 {
 	int sz = __compiletime_object_size(to);
-	int ret = -EFAULT;
 
 	might_fault();
 	if (likely(sz == -1 || sz >= n))
-		ret = _copy_from_user(to, from, n);
+		n = _copy_from_user(to, from, n);
 #ifdef CONFIG_DEBUG_VM
 	else
 		WARN(1, "Buffer overflow detected!\n");
 #endif
-	return ret;
+	return n;
 }
 
 static __always_inline __must_check
--
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