From: Jeff Mahoney <jeffm@suse.com>
Date: Tue, 5 Jul 2016 21:32:30 +0000 (-0400)
Subject: ecryptfs: don't allow mmap when the lower fs doesn't support it
X-Git-Tag: v4.1.12-92~41^2
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=55a5161a5698db10ff75a2de66d8c8913788bb77;p=users%2Fjedix%2Flinux-maple.git

ecryptfs: don't allow mmap when the lower fs doesn't support it

There are legitimate reasons to disallow mmap on certain files, notably
in sysfs or procfs.  We shouldn't emulate mmap support on file systems
that don't offer support natively.

CVE-2016-1583

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Cc: stable@vger.kernel.org
[tyhicks: clean up f_op check by using ecryptfs_file_to_lower()]
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>

Mainline v4.7 commit f0fe970df3838c202ef6c07a4c2b36838ef0a88b
Replaces UEK4 commit e06914f2e9ac6b3f19d4461cb24b401f77ce4f17
which was reverted by UEK4 commit b1660e855b21.

Orabug: 24971905
CVE: CVE-2016-1583
Signed-off-by: Chuck Anderson <chuck.anderson@oracle.com
---

diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
index 72afcc629d7b..f56a4216d081 100644
--- a/fs/ecryptfs/file.c
+++ b/fs/ecryptfs/file.c
@@ -170,6 +170,19 @@ out:
 	return rc;
 }
 
+static int ecryptfs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct file *lower_file = ecryptfs_file_to_lower(file);
+	/*
+	 * Don't allow mmap on top of file systems that don't support it
+	 * natively.  If FILESYSTEM_MAX_STACK_DEPTH > 2 or ecryptfs
+	 * allows recursive mounting, this will need to be extended.
+	 */
+	if (!lower_file->f_op->mmap)
+		return -ENODEV;
+	return generic_file_mmap(file, vma);
+}
+
 /**
  * ecryptfs_open
  * @inode: inode speciying file to open
@@ -365,7 +378,7 @@ const struct file_operations ecryptfs_main_fops = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl = ecryptfs_compat_ioctl,
 #endif
-	.mmap = generic_file_mmap,
+	.mmap = ecryptfs_mmap,
 	.open = ecryptfs_open,
 	.flush = ecryptfs_flush,
 	.release = ecryptfs_release,