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-rw-r--r--fs/eventfd.c67
1 files changed, 54 insertions, 13 deletions
diff --git a/fs/eventfd.c b/fs/eventfd.c
index 31d12de83a2..8b47e4200e6 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -68,11 +68,16 @@ int eventfd_signal(struct eventfd_ctx *ctx, int n)
}
EXPORT_SYMBOL_GPL(eventfd_signal);
+static void eventfd_free_ctx(struct eventfd_ctx *ctx)
+{
+ kfree(ctx);
+}
+
static void eventfd_free(struct kref *kref)
{
struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);
- kfree(ctx);
+ eventfd_free_ctx(ctx);
}
/**
@@ -298,9 +303,23 @@ struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
}
EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
-SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
+/**
+ * eventfd_file_create - Creates an eventfd file pointer.
+ * @count: Initial eventfd counter value.
+ * @flags: Flags for the eventfd file.
+ *
+ * This function creates an eventfd file pointer, w/out installing it into
+ * the fd table. This is useful when the eventfd file is used during the
+ * initialization of data structures that require extra setup after the eventfd
+ * creation. So the eventfd creation is split into the file pointer creation
+ * phase, and the file descriptor installation phase.
+ * In this way races with userspace closing the newly installed file descriptor
+ * can be avoided.
+ * Returns an eventfd file pointer, or a proper error pointer.
+ */
+struct file *eventfd_file_create(unsigned int count, int flags)
{
- int fd;
+ struct file *file;
struct eventfd_ctx *ctx;
/* Check the EFD_* constants for consistency. */
@@ -308,26 +327,48 @@ SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
if (flags & ~EFD_FLAGS_SET)
- return -EINVAL;
+ return ERR_PTR(-EINVAL);
ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);
kref_init(&ctx->kref);
init_waitqueue_head(&ctx->wqh);
ctx->count = count;
ctx->flags = flags;
- /*
- * When we call this, the initialization must be complete, since
- * anon_inode_getfd() will install the fd.
- */
- fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx,
- flags & EFD_SHARED_FCNTL_FLAGS);
- if (fd < 0)
- kfree(ctx);
+ file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx,
+ flags & EFD_SHARED_FCNTL_FLAGS);
+ if (IS_ERR(file))
+ eventfd_free_ctx(ctx);
+
+ return file;
+}
+
+SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
+{
+ int fd, error;
+ struct file *file;
+
+ error = get_unused_fd_flags(flags & EFD_SHARED_FCNTL_FLAGS);
+ if (error < 0)
+ return error;
+ fd = error;
+
+ file = eventfd_file_create(count, flags);
+ if (IS_ERR(file)) {
+ error = PTR_ERR(file);
+ goto err_put_unused_fd;
+ }
+ fd_install(fd, file);
+
return fd;
+
+err_put_unused_fd:
+ put_unused_fd(fd);
+
+ return error;
}
SYSCALL_DEFINE1(eventfd, unsigned int, count)