Patch "ecryptfs: forbid opening files without mmap handler" has been added to the 4.6-stable tree

This is a note to let you know that I've just added the patch titled

ecryptfs: forbid opening files without mmap handler

to the 4.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ecryptfs-forbid-opening-files-without-mmap-handler.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jann Horn <[email protected]>
Date: Wed, 1 Jun 2016 11:55:06 +0200
Subject: ecryptfs: forbid opening files without mmap handler

From: Jann Horn <[email protected]>

commit 2f36db71009304b3f0b95afacd8eba1f9f046b87 upstream.

This prevents users from triggering a stack overflow through a recursive invocation of pagefault handling that involves mapping procfs files into virtual memory.

---
 fs/ecryptfs/kthread.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

@@ -25,6 +25,7 @@
 #include <linux/slab.h>
 #include <linux/wait.h>
 #include <linux/mount.h>
+#include <linux/file.h>
 #include "ecryptfs_kernel.h"
 
 struct ecryptfs_open_req {

@@ -147,7 +148,7 @@ int ecryptfs_privileged_open(struct file
 	flags |= IS_RDONLY(d_inode(lower_dentry)) ? O_RDONLY : O_RDWR;
 	(*lower_file) = dentry_open(&req.path, flags, cred);
 	if (!IS_ERR(*lower_file))
-		goto out;
+		goto have_file;
 	if ((flags & O_ACCMODE) == O_RDONLY) {
 		rc = PTR_ERR((*lower_file));
 		goto out;

@@ -165,8 +166,16 @@ int ecryptfs_privileged_open(struct file
 	mutex_unlock(&ecryptfs_kthread_ctl.mux);
 	wake_up(&ecryptfs_kthread_ctl.wait);
 	wait_for_completion(&req.done);
-	if (IS_ERR(*lower_file))
+	if (IS_ERR(*lower_file)) {
 		rc = PTR_ERR(*lower_file);
+		goto out;
+	}
+have_file:
+	if ((*lower_file)->f_op->mmap == NULL) {
+		fput(*lower_file);
+		*lower_file = NULL;
+		rc = -EMEDIUMTYPE;
+	}
 out:
 	return rc;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.6/ecryptfs-forbid-opening-files-without-mmap-handler.patch queue-4.6/sched-panic-on-corrupted-stack-end.patch queue-4.6/proc-prevent-stacking-filesystems-on-top.patch