1 files changed, 45 insertions, 18 deletions

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 1c8b55670804..da72250ddc1c 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -346,7 +346,7 @@ static inline struct epitem *ep_item_from_epqueue(poll_table *p)
 /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
 static inline int ep_op_has_event(int op)
 {
-        return op != EPOLL_CTL_DEL;
+        return op == EPOLL_CTL_ADD || op == EPOLL_CTL_MOD;
 }
 
 /* Initialize the poll safe wake up structure */
@@ -676,6 +676,34 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi)
         return 0;
 }
 
+/*
+ * Disables a "struct epitem" in the eventpoll set. Returns -EBUSY if the item
+ * had no event flags set, indicating that another thread may be currently
+ * handling that item's events (in the case that EPOLLONESHOT was being
+ * used). Otherwise a zero result indicates that the item has been disabled
+ * from receiving events. A disabled item may be re-enabled via
+ * EPOLL_CTL_MOD. Must be called with "mtx" held.
+ */
+static int ep_disable(struct eventpoll *ep, struct epitem *epi)
+{
+        int result = 0;
+        unsigned long flags;
+
+        spin_lock_irqsave(&ep->lock, flags);
+        if (epi->event.events & ~EP_PRIVATE_BITS) {
+                if (ep_is_linked(&epi->rdllink))
+                        list_del_init(&epi->rdllink);
+                /* Ensure ep_poll_callback will not add epi back onto ready
+                   list: */
+                epi->event.events &= EP_PRIVATE_BITS;
+                }
+        else
+                result = -EBUSY;
+        spin_unlock_irqrestore(&ep->lock, flags);
+
+        return result;
+}
+
 static void ep_free(struct eventpoll *ep)
 {
         struct rb_node *rbp;
@@ -1020,8 +1048,6 @@ static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
         rb_insert_color(&epi->rbn, &ep->rbr);
 }
 
-
-
 #define PATH_ARR_SIZE 5
 /*
  * These are the number paths of length 1 to 5, that we are allowing to emanate
@@ -1654,8 +1680,8 @@ SYSCALL_DEFINE1(epoll_create1, int, flags)
                 error = PTR_ERR(file);
                 goto out_free_fd;
         }
-        fd_install(fd, file);
         ep->file = file;
+        fd_install(fd, file);
         return fd;
 
 out_free_fd:
@@ -1787,6 +1813,12 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
                 } else
                         error = -ENOENT;
                 break;
+        case EPOLL_CTL_DISABLE:
+                if (epi)
+                        error = ep_disable(ep, epi);
+                else
+                        error = -ENOENT;
+                break;
         }
         mutex_unlock(&ep->mtx);
 
@@ -1810,7 +1842,7 @@ SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events,
                 int, maxevents, int, timeout)
 {
         int error;
-        struct file *file;
+        struct fd f;
         struct eventpoll *ep;
 
         /* The maximum number of event must be greater than zero */
@@ -1818,38 +1850,33 @@ SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events,
                 return -EINVAL;
 
         /* Verify that the area passed by the user is writeable */
-        if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) {
-                error = -EFAULT;
-                goto error_return;
-        }
+        if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event)))
+                return -EFAULT;
 
         /* Get the "struct file *" for the eventpoll file */
-        error = -EBADF;
-        file = fget(epfd);
-        if (!file)
-                goto error_return;
+        f = fdget(epfd);
+        if (!f.file)
+                return -EBADF;
 
         /*
          * We have to check that the file structure underneath the fd
          * the user passed to us _is_ an eventpoll file.
          */
         error = -EINVAL;
-        if (!is_file_epoll(file))
+        if (!is_file_epoll(f.file))
                 goto error_fput;
 
         /*
          * At this point it is safe to assume that the "private_data" contains
          * our own data structure.
          */
-        ep = file->private_data;
+        ep = f.file->private_data;
 
         /* Time to fish for events ... */
         error = ep_poll(ep, events, maxevents, timeout);
 
 error_fput:
-        fput(file);
-error_return:
-
+        fdput(f);
         return error;
 }