From: Christian Brauner <brauner@kernel.org>
Date: Thu, 23 Apr 2026 09:56:08 +0000 (+0200)
Subject: eventpoll: move epi_fget() up
X-Git-Tag: v7.1-rc1~33^2^2~5
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=86e87059e6d1fd5115a31949726450ed03c1073b;p=thirdparty%2Fkernel%2Flinux.git

eventpoll: move epi_fget() up

We'll need it when removing files so move it up. No functional change.

Link: https://patch.msgid.link/20260423-work-epoll-uaf-v1-5-2470f9eec0f5@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index f9b601f5c0ad..5ee4398a6cb8 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -826,6 +826,34 @@ static void ep_free(struct eventpoll *ep)
 	kfree_rcu(ep, rcu);
 }
 
+/*
+ * The ffd.file pointer may be in the process of being torn down due to
+ * being closed, but we may not have finished eventpoll_release() yet.
+ *
+ * Normally, even with the atomic_long_inc_not_zero, the file may have
+ * been free'd and then gotten re-allocated to something else (since
+ * files are not RCU-delayed, they are SLAB_TYPESAFE_BY_RCU).
+ *
+ * But for epoll, users hold the ep->mtx mutex, and as such any file in
+ * the process of being free'd will block in eventpoll_release_file()
+ * and thus the underlying file allocation will not be free'd, and the
+ * file re-use cannot happen.
+ *
+ * For the same reason we can avoid a rcu_read_lock() around the
+ * operation - 'ffd.file' cannot go away even if the refcount has
+ * reached zero (but we must still not call out to ->poll() functions
+ * etc).
+ */
+static struct file *epi_fget(const struct epitem *epi)
+{
+	struct file *file;
+
+	file = epi->ffd.file;
+	if (!file_ref_get(&file->f_ref))
+		file = NULL;
+	return file;
+}
+
 /*
  * Called with &file->f_lock held,
  * returns with it released
@@ -1018,34 +1046,6 @@ static __poll_t __ep_eventpoll_poll(struct file *file, poll_table *wait, int dep
 	return res;
 }
 
-/*
- * The ffd.file pointer may be in the process of being torn down due to
- * being closed, but we may not have finished eventpoll_release() yet.
- *
- * Normally, even with the atomic_long_inc_not_zero, the file may have
- * been free'd and then gotten re-allocated to something else (since
- * files are not RCU-delayed, they are SLAB_TYPESAFE_BY_RCU).
- *
- * But for epoll, users hold the ep->mtx mutex, and as such any file in
- * the process of being free'd will block in eventpoll_release_file()
- * and thus the underlying file allocation will not be free'd, and the
- * file re-use cannot happen.
- *
- * For the same reason we can avoid a rcu_read_lock() around the
- * operation - 'ffd.file' cannot go away even if the refcount has
- * reached zero (but we must still not call out to ->poll() functions
- * etc).
- */
-static struct file *epi_fget(const struct epitem *epi)
-{
-	struct file *file;
-
-	file = epi->ffd.file;
-	if (!file_ref_get(&file->f_ref))
-		file = NULL;
-	return file;
-}
-
 /*
  * Differs from ep_eventpoll_poll() in that internal callers already have
  * the ep->mtx so we need to start from depth=1, such that mutex_lock_nested()