[PATCH] NULL pointer dereference in ecryptfs (ecryptfs_setxattr)

[Priya Bansal <p.bansal@samsung.com>]

This patch fixes the issue which was found in
 ecryptfs_setxattr(). Previously, while trying to create a file when ecryptfs
 is mounted over ext4 filesystem  with  encrypted view enabled, the kernel
 crashes. the reason being the function fsstack_copy_attr_all was trying to
 access dentry->d_inode which was null hence the kernel crashes with NULL
 pointer dereference. Now a check has been applied which prevents such
 condition.

From 74856445756aba18f98aa5b98ad46e7d98f54737 Mon Sep 17 00:00:00 2001
From: Priya Bansal <p.bansal@samsung.com>
Date: Fri, 29 Aug 2014 10:27:27 +0530
Subject: [PATCH] Fix in ecryptfs_setxattr for NULL check before calling
 fsstack_copy_attr_all. This patch fixes the issue which was found in
 ecryptfs_setxattr(). Previously, while trying to create a file when ecryptfs
 is mounted over ext4 filesystem  with  encrypted view enabled, the kernel
 crashes. the reason being the function fsstack_copy_attr_all was trying to
 access dentry->d_inode which was null hence the kernel crashes with NULL
 pointer dereference. Now a check has been applied which prevents such
 condition.
Signed-off-by: Priya Bansal <p.bansal@samsung.com>
---
 linux-3.16.1/fs/ecryptfs/inode.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/linux-3.16.1/fs/ecryptfs/inode.c b/linux-3.16.1/fs/ecryptfs/inode.c
index d4a9431..7da03e5 100644
--- a/linux-3.16.1/fs/ecryptfs/inode.c
+++ b/linux-3.16.1/fs/ecryptfs/inode.c
@@ -1031,6 +1031,8 @@ ecryptfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 {
  int rc = 0;
  struct dentry *lower_dentry;
+ struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
+  &ecryptfs_superblock_to_private(dentry->d_sb)->mount_crypt_stat;
 
  lower_dentry = ecryptfs_dentry_to_lower(dentry);
  if (!lower_dentry->d_inode->i_op->setxattr) {
@@ -1039,8 +1041,20 @@ ecryptfs_setxattr(struct dentry *dentry, const char *name, const void *value,
  }
 
  rc = vfs_setxattr(lower_dentry, name, value, size, flags);
- if (!rc)
-  fsstack_copy_attr_all(dentry->d_inode, lower_dentry->d_inode);
+ if (!rc) {
+  if (dentry->d_inode == NULL) {
+   if (mount_crypt_stat->flags
+     & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
+    rc = -EPERM;
+   else if (mount_crypt_stat->flags
+     & ECRYPTFS_XATTR_METADATA_ENABLED)
+    goto out;
+  } else {
+   fsstack_copy_attr_all(dentry->d_inode,
+     lower_dentry->d_inode);
+  }
+ }
+
 out:
  return rc;
 }
-- 
1.8.3.2

If you need any other details regarding this contribution, please contact me.  

Thanks & Regards 
Priya Bansal. 
E-mail: p.bansal@samsung.com