1 files changed, 18 insertions, 13 deletions

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 8efb1e10b025..3e64c6502dc8 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -266,21 +266,19 @@ static void proc_sys_prune_dcache(struct ctl_table_header *head)
         struct inode *inode, *prev = NULL;
         struct proc_inode *ei;
 
-        list_for_each_entry(ei, &head->inodes, sysctl_inodes) {
+        rcu_read_lock();
+        list_for_each_entry_rcu(ei, &head->inodes, sysctl_inodes) {
                 inode = igrab(&ei->vfs_inode);
                 if (inode) {
-                        spin_unlock(&sysctl_lock);
+                        rcu_read_unlock();
                         iput(prev);
                         prev = inode;
                         d_prune_aliases(inode);
-                        spin_lock(&sysctl_lock);
+                        rcu_read_lock();
                 }
         }
-        if (prev) {
-                spin_unlock(&sysctl_lock);
-                iput(prev);
-                spin_lock(&sysctl_lock);
-        }
+        rcu_read_unlock();
+        iput(prev);
 }
 
 /* called under sysctl_lock, will reacquire if has to wait */
@@ -296,10 +294,10 @@ static void start_unregistering(struct ctl_table_header *p)
                 p->unregistering = &wait;
                 spin_unlock(&sysctl_lock);
                 wait_for_completion(&wait);
-                spin_lock(&sysctl_lock);
         } else {
                 /* anything non-NULL; we'll never dereference it */
                 p->unregistering = ERR_PTR(-EINVAL);
+                spin_unlock(&sysctl_lock);
         }
         /*
          * Prune dentries for unregistered sysctls: namespaced sysctls
@@ -310,6 +308,7 @@ static void start_unregistering(struct ctl_table_header *p)
          * do not remove from the list until nobody holds it; walking the
          * list in do_sysctl() relies on that.
          */
+        spin_lock(&sysctl_lock);
         erase_header(p);
 }
 
@@ -455,11 +454,17 @@ static struct inode *proc_sys_make_inode(struct super_block *sb,
         inode->i_ino = get_next_ino();
 
         ei = PROC_I(inode);
-        ei->sysctl = head;
-        ei->sysctl_entry = table;
 
         spin_lock(&sysctl_lock);
-        list_add(&ei->sysctl_inodes, &head->inodes);
+        if (unlikely(head->unregistering)) {
+                spin_unlock(&sysctl_lock);
+                iput(inode);
+                inode = NULL;
+                goto out;
+        }
+        ei->sysctl = head;
+        ei->sysctl_entry = table;
+        list_add_rcu(&ei->sysctl_inodes, &head->inodes);
         head->count++;
         spin_unlock(&sysctl_lock);
 
@@ -487,7 +492,7 @@ out:
 void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
 {
         spin_lock(&sysctl_lock);
-        list_del(&PROC_I(inode)->sysctl_inodes);
+        list_del_rcu(&PROC_I(inode)->sysctl_inodes);
         if (!--head->count)
                 kfree_rcu(head, rcu);
         spin_unlock(&sysctl_lock);