lkml.org 
[lkml]   [2016]   [Aug]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] fscrypto: fix to null-terminate encrypted filename in fname_encrypt
From
Date
Hi Ted,

On 2016/8/28 13:13, Theodore Ts'o wrote:
> On Sun, Aug 28, 2016 at 09:13:28AM +0800, Chao Yu wrote:
>> From: Chao Yu <yuchao0@huawei.com>
>>
>> This patch fixes to add null character at the end of encrypted filename
>> in fname_encrypt, in order to avoid incorrectly traversing random data
>> located after target filename. The call stack is as below:
>>
>> - f2fs_add_link
>> - __f2fs_add_link
>> - fscrypt_setup_filename
>> - fscrypt_fname_alloc_buffer allocate buffer for @fname
>> - fname_encrypt didn't set null character for @fname
>> - f2fs_add_regular_entry init qstr with @fname
>> - init_inode_metadata
>> - f2fs_init_security
>> - security_inode_init_security
>> - selinux_inode_init_security
>> - selinux_determine_inode_label
>> - security_transition_sid
>> - security_compute_sid
>> - filename_compute_type
>> - hashtab_search
>> - filenametr_hash traverse @fname as one which has null character
>
> The problem is not in fname_encrypt(), but rather that
> security_inode_init_security() should be given the _unencrypted_
> filename.
>
> In ext4 security_inode_init_security() is called with the qstr from
> the dentry, not the encrypted qstr --- in fact we call
> security_inode_init_security before we call fname_encrypt.
>
> SELinux needs the unencrypted filename in order to decide which
> SELinux rules / labels should apply.

You're right, I missed this mistake. So actually, this is a bug of f2fs.
Let me figure out the fixing patch.

Thanks for your review! :)

Thanks,

>
> - Ted
>

\
 
 \ /
  Last update: 2016-09-17 09:58    [W:0.042 / U:0.280 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site