[patch 17/28] cifs: Fix incorrect destination buffer size in cifs_strncpy_to_host

[Greg KH <gregkh@suse.de>]

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2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Suresh Jayaraman <sjayaraman@suse.de>


Relevant commits 968460ebd8006d55661dec0fb86712b40d71c413 and 
066ce6899484d9026acd6ba3a8dbbedb33d7ae1b. Minimal hunks to fix buffer
size and fix an existing problem pointed out by Guenter Kukuk that length
of src is used for NULL termination of dst. 

cifs: Rename cifs_strncpy_to_host and fix buffer size

There is a possibility for the path_name and node_name buffers to
overflow if they contain charcters that are >2 bytes in the local
charset. Resize the buffer allocation so to avoid this possibility.

Also, as pointed out by Jeff Layton, it would be appropriate to
rename the function to cifs_strlcpy_to_host to reflect the fact
that the copied string is always NULL terminated.

Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 fs/cifs/cifssmb.c |   17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -91,23 +91,22 @@ static int
 cifs_strncpy_to_host(char **dst, const char *src, const int maxlen,
 		 const bool is_unicode, const struct nls_table *nls_codepage)
 {
-	int plen;
+	int src_len, dst_len;
 
 	if (is_unicode) {
-		plen = UniStrnlen((wchar_t *)src, maxlen);
-		*dst = kmalloc(plen + 2, GFP_KERNEL);
+		src_len = UniStrnlen((wchar_t *)src, maxlen);
+		*dst = kmalloc((4 * src_len) + 2, GFP_KERNEL);
 		if (!*dst)
 			goto cifs_strncpy_to_host_ErrExit;
-		cifs_strfromUCS_le(*dst, (__le16 *)src, plen, nls_codepage);
+		dst_len = cifs_strfromUCS_le(*dst, (__le16 *)src, src_len, nls_codepage);
+		(*dst)[dst_len + 1] = 0;
 	} else {
-		plen = strnlen(src, maxlen);
-		*dst = kmalloc(plen + 2, GFP_KERNEL);
+		src_len = strnlen(src, maxlen);
+		*dst = kmalloc(src_len + 1, GFP_KERNEL);
 		if (!*dst)
 			goto cifs_strncpy_to_host_ErrExit;
-		strncpy(*dst, src, plen);
+		strlcpy(*dst, src, src_len + 1);
 	}
-	(*dst)[plen] = 0;
-	(*dst)[plen+1] = 0; /* harmless for ASCII case, needed for Unicode */
 	return 0;
 
 cifs_strncpy_to_host_ErrExit: