On 11/14/19 5:55 AM, Patrick Callaghan wrote:
Hi Patrick,
Hello Laks,
You suggested that the if statement of the patch change to the
following:
if ((rbuf_len == 0) || (offset + rbuf_len >= i_size)) {
Unless the file size changed between the time that i_size was set in
ima_calc_file_hash_tfm() and an i_size_read() call was subsequently
issued in a function downstream of the integrity_kernel_read() call,
the rbuf_len returned on the integrity_kernel_read() call will not be
more than i_size - offset. I do not think that it is possible for the
file size to change during this window but nonetheless, if it can, this
would be a different problem and I would not want to include this in my
patch. That said, I do appreciate you taking time to review this patch.
You are right - unless the file size changes between the calls this
problem would not occur. I agree - that issue, even if it can occur,
should be addressed separately.
Another one (again - am not saying this needs to be addressed in this
patch, but just wanted to point out)
rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
...
rbuf_len = integrity_kernel_read(file, offset, rbuf, PAGE_SIZE);
...
rc = crypto_shash_update(shash, rbuf, rbuf_len);
rbuf is of size PAGE_SIZE, but rbuf_len, returned by
integrity_kernel_read() is passed as buffer size to
crypto_shash_update() without any validation (rbuf_len <= PAGE_SIZE)
It is assumed here that integrity_kernel_read() would not return a
length greater than rbuf size and hence crypto_shash_update() would
never access beyond the given buffer.
thanks,
-lakshmi
