NFS: don't store 'struct cred *' in struct nfs_access_entry

Storing the 'struct cred *' in nfs_access_entry is problematic.
An active 'cred' can keep a 'struct key *' active, and a quota is
imposed on the number of such keys that a user can maintain.
Cached 'nfs_access_entry' structs have indefinite lifetime, and having
these keep 'struct key's alive imposes on that quota.

So remove the 'struct cred *' and replace it with the fields we need:
  kuid_t, kgid_t, and struct group_info *

This makes the 'struct nfs_access_entry' 64 bits larger.

New function "access_cmp" is introduced which is identical to
cred_fscmp() except that the second arg is an 'nfs_access_entry', rather
than a 'cred'

Fixes: b68572e07c58 ("NFS: change access cache to use 'struct cred'.")
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index a34351c..7dee3fd 100644 (file)
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -2528,7 +2528,7 @@ MODULE_PARM_DESC(nfs_access_max_cachesize, "NFS access maximum total cache lengt
 
 static void nfs_access_free_entry(struct nfs_access_entry *entry)
 {
-       put_cred(entry->cred);
+       put_group_info(entry->group_info);
        kfree_rcu(entry, rcu_head);
        smp_mb__before_atomic();
        atomic_long_dec(&nfs_access_nr_entries);
@@ -2654,6 +2654,43 @@ void nfs_access_zap_cache(struct inode *inode)
 }
 EXPORT_SYMBOL_GPL(nfs_access_zap_cache);
 
+static int access_cmp(const struct cred *a, const struct nfs_access_entry *b)
+{
+       struct group_info *ga, *gb;
+       int g;
+
+       if (uid_lt(a->fsuid, b->fsuid))
+               return -1;
+       if (uid_gt(a->fsuid, b->fsuid))
+               return 1;
+
+       if (gid_lt(a->fsgid, b->fsgid))
+               return -1;
+       if (gid_gt(a->fsgid, b->fsgid))
+               return 1;
+
+       ga = a->group_info;
+       gb = b->group_info;
+       if (ga == gb)
+               return 0;
+       if (ga == NULL)
+               return -1;
+       if (gb == NULL)
+               return 1;
+       if (ga->ngroups < gb->ngroups)
+               return -1;
+       if (ga->ngroups > gb->ngroups)
+               return 1;
+
+       for (g = 0; g < ga->ngroups; g++) {
+               if (gid_lt(ga->gid[g], gb->gid[g]))
+                       return -1;
+               if (gid_gt(ga->gid[g], gb->gid[g]))
+                       return 1;
+       }
+       return 0;
+}
+
 static struct nfs_access_entry *nfs_access_search_rbtree(struct inode *inode, const struct cred *cred)
 {
        struct rb_node *n = NFS_I(inode)->access_cache.rb_node;
@@ -2661,7 +2698,7 @@ static struct nfs_access_entry *nfs_access_search_rbtree(struct inode *inode, co
        while (n != NULL) {
                struct nfs_access_entry *entry =
                        rb_entry(n, struct nfs_access_entry, rb_node);
-               int cmp = cred_fscmp(cred, entry->cred);
+               int cmp = access_cmp(cred, entry);
 
                if (cmp < 0)
                        n = n->rb_left;
@@ -2731,7 +2768,7 @@ static int nfs_access_get_cached_rcu(struct inode *inode, const struct cred *cre
        lh = rcu_dereference(list_tail_rcu(&nfsi->access_cache_entry_lru));
        cache = list_entry(lh, struct nfs_access_entry, lru);
        if (lh == &nfsi->access_cache_entry_lru ||
-           cred_fscmp(cred, cache->cred) != 0)
+           access_cmp(cred, cache) != 0)
                cache = NULL;
        if (cache == NULL)
                goto out;
@@ -2773,7 +2810,7 @@ static void nfs_access_add_rbtree(struct inode *inode,
        while (*p != NULL) {
                parent = *p;
                entry = rb_entry(parent, struct nfs_access_entry, rb_node);
-               cmp = cred_fscmp(cred, entry->cred);
+               cmp = access_cmp(cred, entry);
 
                if (cmp < 0)
                        p = &parent->rb_left;
@@ -2802,7 +2839,9 @@ void nfs_access_add_cache(struct inode *inode, struct nfs_access_entry *set,
        if (cache == NULL)
                return;
        RB_CLEAR_NODE(&cache->rb_node);
-       cache->cred = get_cred(cred);
+       cache->fsuid = cred->fsuid;
+       cache->fsgid = cred->fsgid;
+       cache->group_info = get_group_info(cred->group_info);
        cache->mask = set->mask;
 
        /* The above field assignments must be visible
@@ -2895,7 +2934,6 @@ static int nfs_do_access(struct inode *inode, const struct cred *cred, int mask)
                cache.mask |= NFS_ACCESS_DELETE | NFS_ACCESS_LOOKUP;
        else
                cache.mask |= NFS_ACCESS_EXECUTE;
-       cache.cred = cred;
        status = NFS_PROTO(inode)->access(inode, &cache, cred);
        if (status != 0) {
                if (status == -ESTALE) {

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index f02aa98..5d9ff01 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2653,7 +2653,6 @@ static int nfs4_opendata_access(const struct cred *cred,
        } else if ((fmode & FMODE_READ) && !opendata->file_created)
                mask = NFS4_ACCESS_READ;
 
-       cache.cred = cred;
        nfs_access_set_mask(&cache, opendata->o_res.access_result);
        nfs_access_add_cache(state->inode, &cache, cred);
 

diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index c33b1b7..450e393 100644 (file)
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -61,7 +61,9 @@
 struct nfs_access_entry {
        struct rb_node          rb_node;
        struct list_head        lru;
-       const struct cred *     cred;
+       kuid_t                  fsuid;
+       kgid_t                  fsgid;
+       struct group_info       *group_info;
        __u32                   mask;
        struct rcu_head         rcu_head;
 };