[RFC PATCH 03/11] mm/mempolicy: refactor sanitize_mpol_flags for reuse

[Gregory Price <gourry.memverge@gmail.com>]

split sanitize_mpol_flags into sanitize and validate.

Sanitize is used by set_mempolicy to split (int mode) into mode
and mode_flags, and then validates them.

Validate validates already split flags.

Validate will be reused for new syscalls that accept already
split mode and mode_flags.

Signed-off-by: Gregory Price <gregory.price@memverge.com>
---
 mm/mempolicy.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 65e0334a1a18..eec807d0c6a1 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1466,24 +1466,39 @@ static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode,
 	return copy_to_user(mask, nodes_addr(*nodes), copy) ? -EFAULT : 0;
 }
 
-/* Basic parameter sanity check used by both mbind() and set_mempolicy() */
-static inline int sanitize_mpol_flags(int *mode, unsigned short *flags)
+/*
+ * Basic parameter sanity check used by mbind/set_mempolicy
+ * May modify flags to include internal flags (e.g. MPOL_F_MOF/F_MORON)
+ */
+static inline int validate_mpol_flags(unsigned short mode, unsigned short *flags)
 {
-	*flags = *mode & MPOL_MODE_FLAGS;
-	*mode &= ~MPOL_MODE_FLAGS;
-
-	if ((unsigned int)(*mode) >=  MPOL_MAX)
+	if ((unsigned int)(mode) >= MPOL_MAX)
 		return -EINVAL;
 	if ((*flags & MPOL_F_STATIC_NODES) && (*flags & MPOL_F_RELATIVE_NODES))
 		return -EINVAL;
 	if (*flags & MPOL_F_NUMA_BALANCING) {
-		if (*mode != MPOL_BIND)
+		if (mode != MPOL_BIND)
 			return -EINVAL;
 		*flags |= (MPOL_F_MOF | MPOL_F_MORON);
 	}
 	return 0;
 }
 
+/*
+ * Used by mbind/set_memplicy to split and validate mode/flags
+ * set_mempolicy combines (mode | flags), split them out into separate
+ * fields and return just the mode in mode_arg and flags in flags.
+ */
+static inline int sanitize_mpol_flags(int *mode_arg, unsigned short *flags)
+{
+	unsigned short mode = (*mode_arg & ~MPOL_MODE_FLAGS);
+
+	*flags = *mode_arg & MPOL_MODE_FLAGS;
+	*mode_arg = mode;
+
+	return validate_mpol_flags(mode, flags);
+}
+
 static long kernel_mbind(unsigned long start, unsigned long len,
 			 unsigned long mode, const unsigned long __user *nmask,
 			 unsigned long maxnode, unsigned int flags)
-- 
2.39.1