1 files changed, 65 insertions, 16 deletions

diff --git a/fs/fcntl.c b/fs/fcntl.c
index 9d175d623aab..ecc8b3954ed6 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -640,7 +640,7 @@ static void fasync_free_rcu(struct rcu_head *head)
  * match the state "is the filp on a fasync list".
  *
  */
-static int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
+int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
 {
         struct fasync_struct *fa, **fp;
         int result = 0;
@@ -666,21 +666,31 @@ static int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
         return result;
 }
 
+struct fasync_struct *fasync_alloc(void)
+{
+        return kmem_cache_alloc(fasync_cache, GFP_KERNEL);
+}
+
 /*
- * Add a fasync entry. Return negative on error, positive if
- * added, and zero if did nothing but change an existing one.
+ * NOTE! This can be used only for unused fasync entries:
+ * entries that actually got inserted on the fasync list
+ * need to be released by rcu - see fasync_remove_entry.
+ */
+void fasync_free(struct fasync_struct *new)
+{
+        kmem_cache_free(fasync_cache, new);
+}
+
+/*
+ * Insert a new entry into the fasync list.  Return the pointer to the
+ * old one if we didn't use the new one.
  *
  * NOTE! It is very important that the FASYNC flag always
  * match the state "is the filp on a fasync list".
  */
-static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
+struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasync_struct **fapp, struct fasync_struct *new)
 {
-        struct fasync_struct *new, *fa, **fp;
-        int result = 0;
-
-        new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
-        if (!new)
-                return -ENOMEM;
+        struct fasync_struct *fa, **fp;
 
         spin_lock(&filp->f_lock);
         spin_lock(&fasync_lock);
@@ -691,8 +701,6 @@ static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fa
                 spin_lock_irq(&fa->fa_lock);
                 fa->fa_fd = fd;
                 spin_unlock_irq(&fa->fa_lock);
-
-                kmem_cache_free(fasync_cache, new);
                 goto out;
         }
 
@@ -702,13 +710,39 @@ static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fa
         new->fa_fd = fd;
         new->fa_next = *fapp;
         rcu_assign_pointer(*fapp, new);
-        result = 1;
         filp->f_flags |= FASYNC;
 
 out:
         spin_unlock(&fasync_lock);
         spin_unlock(&filp->f_lock);
-        return result;
+        return fa;
+}
+
+/*
+ * Add a fasync entry. Return negative on error, positive if
+ * added, and zero if did nothing but change an existing one.
+ */
+static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
+{
+        struct fasync_struct *new;
+
+        new = fasync_alloc();
+        if (!new)
+                return -ENOMEM;
+
+        /*
+         * fasync_insert_entry() returns the old (update) entry if
+         * it existed.
+         *
+         * So free the (unused) new entry and return 0 to let the
+         * caller know that we didn't add any new fasync entries.
+         */
+        if (fasync_insert_entry(fd, filp, fapp, new)) {
+                fasync_free(new);
+                return 0;
+        }
+
+        return 1;
 }
 
 /*
@@ -767,11 +801,26 @@ void kill_fasync(struct fasync_struct **fp, int sig, int band)
 }
 EXPORT_SYMBOL(kill_fasync);
 
-static int __init fasync_init(void)
+static int __init fcntl_init(void)
 {
+        /*
+         * Please add new bits here to ensure allocation uniqueness.
+         * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
+         * is defined as O_NONBLOCK on some platforms and not on others.
+         */
+        BUILD_BUG_ON(18 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
+                O_RDONLY        | O_WRONLY      | O_RDWR        |
+                O_CREAT         | O_EXCL        | O_NOCTTY      |
+                O_TRUNC         | O_APPEND      | /* O_NONBLOCK | */
+                __O_SYNC        | O_DSYNC       | FASYNC        |
+                O_DIRECT        | O_LARGEFILE   | O_DIRECTORY   |
+                O_NOFOLLOW      | O_NOATIME     | O_CLOEXEC     |
+                FMODE_EXEC
+                ));
+
         fasync_cache = kmem_cache_create("fasync_cache",
                 sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
         return 0;
 }
 
-module_init(fasync_init)
+module_init(fcntl_init)