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CIFS: fix wrapping bugs in num_entries() 

The problem is that "entryptr + next_offset" and "entryptr + len + size"
can wrap.  I ended up changing the type of "entryptr" because it makes
the math easier when we don't have to do so much casting.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
CC: Stable <stable@vger.kernel.org>
This commit is contained in:
Dan Carpenter 2018-09-06 12:48:22 +03:00 committed by Steve French
parent 8ad8aa3535
commit 56446f218a
1 changed files with 15 additions and 10 deletions
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25
fs/cifs/smb2pdu.c
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@ -3577,33 +3577,38 @@ num_entries(char *bufstart, char *end_of_buf, char **lastentry, size_t size)
int len;
unsigned int entrycount = 0;
unsigned int next_offset = 0;
FILE_DIRECTORY_INFO *entryptr;
char *entryptr;
FILE_DIRECTORY_INFO *dir_info;
if (bufstart == NULL)
return 0;
entryptr = (FILE_DIRECTORY_INFO *)bufstart;
entryptr = bufstart;
while (1) {
entryptr = (FILE_DIRECTORY_INFO *)
((char *)entryptr + next_offset);
if ((char *)entryptr + size > end_of_buf) {
if (entryptr + next_offset < entryptr ||
entryptr + next_offset > end_of_buf ||
entryptr + next_offset + size > end_of_buf) {
cifs_dbg(VFS, "malformed search entry would overflow\n");
break;
}
len = le32_to_cpu(entryptr->FileNameLength);
if ((char *)entryptr + len + size > end_of_buf) {
entryptr = entryptr + next_offset;
dir_info = (FILE_DIRECTORY_INFO *)entryptr;
len = le32_to_cpu(dir_info->FileNameLength);
if (entryptr + len < entryptr ||
entryptr + len > end_of_buf ||
entryptr + len + size > end_of_buf) {
cifs_dbg(VFS, "directory entry name would overflow frame end of buf %p\n",
end_of_buf);
break;
}
*lastentry = (char *)entryptr;
*lastentry = entryptr;
entrycount++;
next_offset = le32_to_cpu(entryptr->NextEntryOffset);
next_offset = le32_to_cpu(dir_info->NextEntryOffset);
if (!next_offset)
break;
}