Pekka Enberg wrote:
Hi Patrick,
Patrick McHardy wrote:
> I think you are misunderstanding ksize() (see mm/slub.c::ksize() for
> example).
The ksize() description in mm/slab.c matches exactly what netfilter
wants to do:
Agreed.
Patrick McHardy wrote:
The initial allocation size is calculated as max(size, min slab size)
and is stored as ext->alloc_size. When adding the first extension,
Yes, this part is correct, however...
it allocates ext->alloc_size of memory and stores both the real amount
of space used (ext->len) and the actual size (ext->real_len).
When adding further extensions, it calculates the new total amount of
space needed (newlen). If that is larger than the real amount of
memory allocated (real_len), it reallocates.
...looking at nf_ct_ext_create() you do:
*ext = kzalloc(real_len, gfp);
^^^^^^^^
if (!*ext)
return NULL;
(*ext)->offset[id] = off;
(*ext)->len = len;
(*ext)->real_len = real_len;
^^^^^^^^
You are storing the _object size_ (total amount of memory requested) and
not the _buffer size_ (total amount of memory allocated). Keep in mind
that object size < buffer size and that ksize() returns the latter.
For all length <= minimum slab size alloc_size (and thus
real_len) is equal to the buffer size. You are correct
however that your patch is fine, I somehow misread the
+ if (newlen >= ksize(ct->ext)) {
part and thought you would always compare against the
minimum slab size.
I've queued your patch and will pass it upstream after
some testing, thanks.
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