linux-kernel - [PATCH] fscrypto: fix to null-terminate encrypted filename in fname

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Date:   Sun, 28 Aug 2016 09:13:28 +0800
From:   Chao Yu <chao@...nel.org>
To:     tytso@....edu, jaegeuk@...nel.org
Cc:     linux-f2fs-devel@...ts.sourceforge.net, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, Chao Yu <yuchao0@...wei.com>
Subject: [PATCH] fscrypto: fix to null-terminate encrypted filename in fname_encrypt

From: Chao Yu <yuchao0@...wei.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

Signed-off-by: Chao Yu <yuchao0@...wei.com>
---
 fs/crypto/fname.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
index 5d6d491..5c356c0 100644
--- a/fs/crypto/fname.c
+++ b/fs/crypto/fname.c
@@ -110,6 +110,7 @@ static int fname_encrypt(struct inode *inode,
 				"%s: Error (error code %d)\n", __func__, res);
 
 	oname->len = ciphertext_len;
+	oname->name[oname->len] = 0;
 	return res;
 }
 
-- 
2.7.2