Greg Kroah-Hartman <gre...@linuxfoundation.org> wrote: > On Thu, May 17, 2018 at 12:42:00PM +0200, Jan Engelhardt wrote: > > > > On Thursday 2018-05-17 12:09, Greg Kroah-Hartman wrote: > > >> > --- a/net/netfilter/x_tables.c > > >> > +++ b/net/netfilter/x_tables.c > > >> > @@ -1183,11 +1183,10 @@ struct xt_table_info > > >> > *xt_alloc_table_info(unsigned int size) > > >> > * than shoot all processes down before realizing there is > > >> > nothing > > >> > * more to reclaim. > > >> > */ > > >> > - info = kvmalloc(sz, GFP_KERNEL | __GFP_NORETRY); > > >> > + info = kvzalloc(sz, GFP_KERNEL | __GFP_NORETRY); > > >> > if (!info) > > >> > return NULL; > > >> > > >> I am curious, what particular path does not later overwrite the whole > > >> zone ? > > > > > >In do_ipt_get_ctl, the IPT_SO_GET_ENTRIES: option uses a len value that > > >can be larger than the size of the structure itself. > > > > > >Then the data is copied to userspace in copy_entries_to_user() for ipv4 > > >and v6, and that's where the "bad data" > > > > If the kernel incorrectly copies more bytes than it should, isn't that > > a sign that may be going going past the end of the info buffer? > > (And thus, zeroing won't truly fix the issue) > > No, the buffer size is correct, we just aren't filling up the whole > buffer as the data requested is smaller than the buffer size.
I have no objections to the patch but I'd like to understand what problem its fixing. Normal pattern is: newinfo = xt_alloc_table_info(tmp.size); copy_from_user(newinfo->entries, user + sizeof(tmp), tmp.size); So inital value of the rule blob area should not matter. Furthermore, when copying the rule blob back to userspace, the kernel is not supposed to copy any padding back to userspace either, since commit f32815d21d4d8287336fb9cef4d2d9e0866214c2 only the user-relevant parts should be copied (some matches and targets allocate kernel-private data such as pointers, and we did use to leak such pointer values back to userspace). -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
