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Subject[PATCH v3 1/5] uaccess: Add user_access_ok()
Date
From: Peter Zijlstra <peterz@infradead.org>

Add user_access_ok() macro which ensures current context
is user context, or explicitly do set_fs(USER_DS).

This function is very much like access_ok(), except it (may)
have different context validation. In general we must be
very careful when using this.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/x86/include/asm/uaccess.h | 8 +++++++-
include/linux/uaccess.h | 18 ++++++++++++++++++
2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 780f2b42c8ef..3125d129d3b6 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -92,12 +92,18 @@ static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, un
* checks that the pointer is in the user space range - after calling
* this function, memory access functions may still return -EFAULT.
*/
-#define access_ok(addr, size) \
+#define access_ok(addr, size) \
({ \
WARN_ON_IN_IRQ(); \
likely(!__range_not_ok(addr, size, user_addr_max())); \
})

+#define user_access_ok(addr, size) \
+({ \
+ WARN_ON_ONCE(!segment_eq(get_fs(), USER_DS)); \
+ likely(!__range_not_ok(addr, size, user_addr_max())); \
+})
+
/*
* These are the main single-value transfer routines. They automatically
* use the right size if we just have the right pointer type.
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 37b226e8df13..bf762689658b 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -10,6 +10,24 @@

#include <asm/uaccess.h>

+/**
+ * user_access_ok: Checks if a user space pointer is valid
+ * @addr: User space pointer to start of block to check
+ * @size: Size of block to check
+ *
+ * Context: User context or explicit set_fs(USER_DS).
+ *
+ * This function is very much like access_ok(), except it (may) have different
+ * context validation. In general we must be very careful when using this.
+ */
+#ifndef user_access_ok
+#define user_access_ok(addr, size) \
+({ \
+ WARN_ON_ONCE(!segment_eq(get_fs(), USER_DS)); \
+ access_ok(addr, size); \
+})
+#endif
+
/*
* Architectures should provide two primitives (raw_copy_{to,from}_user())
* and get rid of their private instances of copy_{to,from}_user() and
\
 
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