[PATCH] kernel/groups.c: consider about NULL for 'group_info' inall related extern functions

[Chen Gang]

groups_alloc() can return NULL for 'group_info', also group_search()
already considers about NULL for 'group_info', so can assume the caller
has right to use all related extern functions when 'group_info' is NULL.

For groups_free(), need check NULL to match groups_alloc(), just like
kmalloc/free().

For set_groups(), can allow the caller to set NULL parameter to new
'cred'.

For system call getgroups(), if 'cred->group_info' is NULL, need return
the related error code (no related data), also need change the related
man page ("man 2 getgroups") to complete the return value.


Signed-off-by: Chen Gang <gang.chen@xxxxxxxxxxx>
---
 kernel/groups.c |   14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/kernel/groups.c b/kernel/groups.c
index 6b2588d..a21a4ce 100644
--- a/kernel/groups.c
+++ b/kernel/groups.c
@@ -52,6 +52,9 @@ EXPORT_SYMBOL(groups_alloc);

 void groups_free(struct group_info *group_info)
 {
+	if (!group_info)
+		return;
+
 	if (group_info->blocks[0] != group_info->small_block) {
 		int i;
 		for (i = 0; i < group_info->nblocks; i++)
@@ -163,9 +166,12 @@ int groups_search(const struct group_info
*group_info, kgid_t grp)
  */
 int set_groups(struct cred *new, struct group_info *group_info)
 {
-	put_group_info(new->group_info);
-	groups_sort(group_info);
-	get_group_info(group_info);
+	if (new->group_info)
+		put_group_info(new->group_info);
+	if (group_info) {
+		groups_sort(group_info);
+		get_group_info(group_info);
+	}
 	new->group_info = group_info;
 	return 0;
 }
@@ -206,6 +212,8 @@ SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t
__user *, grouplist)

 	if (gidsetsize < 0)
 		return -EINVAL;
+	if (!cred->group_info)
+		return -ENODATA;

 	/* no need to grab task_lock here; it cannot change */
 	i = cred->group_info->ngroups;
-- 
1.7.7.6
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