eCryptfs: Clear buffer before reading in metadata xattr

We initially read in the first PAGE_CACHE_SIZE of a file to if the
eCryptfs header marker can be found.  If it isn't found and
ecryptfs_xattr_metadata was given as a mount option, then the
user.ecryptfs xattr is read into the same buffer.  Since the data from
the first page of the file wasn't cleared, it is possible that we think
we've found a second tag 3 or tag 1 packet and then error out after the
packet contents aren't as expected.  This patch clears the buffer before
filling it with metadata from the user.ecryptfs xattr.

Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index a50efb18701c..ddbd096c7406 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -323,6 +323,7 @@ int ecryptfs_lookup_and_interpose_lower(struct dentry *ecryptfs_dentry,
         rc = ecryptfs_read_and_validate_header_region(page_virt,
                                                       ecryptfs_dentry->d_inode);
         if (rc) {
+                memset(page_virt, 0, PAGE_CACHE_SIZE);
                 rc = ecryptfs_read_and_validate_xattr_region(page_virt,
                                                              ecryptfs_dentry);
                 if (rc) {