[PATH v3 net-next] net: remove member 'max' of struct scm_fp_list

[yuan linyu]

From: yuan linyu <linyu.y...@alcatel-sbell.com.cn>

'max' only used at three places in scm.c,
1. in scm_fp_copy(), fpl->max = SCM_MAX_FD;
2. in scm_fp_copy(), if (fpl->count + num > fpl->max)
3. in scm_fp_dup(), new_fpl->max = new_fpl->count;
at place 3, the worst case is new_fpl->count = SCM_MAX_FD,
so do a full size dup, then 'max' field will always
SCM_MAX_FD and it can be removed.

Signed-off-by: yuan linyu <linyu.y...@alcatel-sbell.com.cn>
---
v2->v3:
        change scm_fp_dup() to do a full size dup

v1->v2:
        update commit log to describe correct reason to remove 'max'

 include/net/scm.h |  3 +--
 net/core/scm.c    | 23 ++++++-----------------
 2 files changed, 7 insertions(+), 19 deletions(-)

diff --git a/include/net/scm.h b/include/net/scm.h
index 59fa93c..1301227 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -19,8 +19,7 @@ struct scm_creds {
 };
 
 struct scm_fp_list {
-       short                   count;
-       short                   max;
+       unsigned int    count;
        struct user_struct      *user;
        struct file             *fp[SCM_MAX_FD];
 };
diff --git a/net/core/scm.c b/net/core/scm.c
index b6d8368..fb3ab32 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -69,15 +69,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct 
scm_fp_list **fplp)
        int *fdp = (int*)CMSG_DATA(cmsg);
        struct scm_fp_list *fpl = *fplp;
        struct file **fpp;
-       int i, num;
-
-       num = (cmsg->cmsg_len - sizeof(struct cmsghdr))/sizeof(int);
-
-       if (num <= 0)
-               return 0;
-
-       if (num > SCM_MAX_FD)
-               return -EINVAL;
+       unsigned int i, num;
 
        if (!fpl)
        {
@@ -86,18 +78,17 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct 
scm_fp_list **fplp)
                        return -ENOMEM;
                *fplp = fpl;
                fpl->count = 0;
-               fpl->max = SCM_MAX_FD;
                fpl->user = NULL;
        }
-       fpp = &fpl->fp[fpl->count];
 
-       if (fpl->count + num > fpl->max)
+       num = (cmsg->cmsg_len - sizeof(struct cmsghdr))/sizeof(int);
+       if (fpl->count + num > SCM_MAX_FD)
                return -EINVAL;
 
        /*
         *      Verify the descriptors and increment the usage count.
         */
-
+       fpp = &fpl->fp[fpl->count];
        for (i=0; i< num; i++)
        {
                int fd = fdp[i];
@@ -112,7 +103,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct 
scm_fp_list **fplp)
        if (!fpl->user)
                fpl->user = get_uid(current_user());
 
-       return num;
+       return 0;
 }
 
 void __scm_destroy(struct scm_cookie *scm)
@@ -336,12 +327,10 @@ struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
        if (!fpl)
                return NULL;
 
-       new_fpl = kmemdup(fpl, offsetof(struct scm_fp_list, fp[fpl->count]),
-                         GFP_KERNEL);
+       new_fpl = kmemdup(fpl, sizeof(*fpl), GFP_KERNEL);
        if (new_fpl) {
                for (i = 0; i < fpl->count; i++)
                        get_file(fpl->fp[i]);
-               new_fpl->max = new_fpl->count;
                new_fpl->user = get_uid(fpl->user);
        }
        return new_fpl;
-- 
2.7.4