On Tue, Jun 28, 2022 at 10:36:51AM -0300, Jason Gunthorpe wrote:
On Tue, Jun 28, 2022 at 04:21:29AM +0200, Gustavo A. R. Silva wrote:
Though maybe we could just switch off -Wgnu-variable-sized-type-not-at-end during configuration ?
We need to think in a different strategy.
I think we will need to switch off the warning in userspace - this is
doable for rdma-core.
On the other hand, if the goal is to enable the array size check
compiler warning I would suggest focusing only on those structs that
actually hit that warning in the kernel. IIRC infiniband doesn't
trigger it because it just pointer casts the flex array to some other
struct.
Yep; this is actually why I reverted those changes in rdma (before
sending out the patch) when 0-day reported the same problems you pointed
out[1].
Also, that's the strategy I'm following right now with the one-element
array into flex-array member transformations. I'm addressing those cases
in which the trailing array is actually being iterated over, first.
I just added the patch to my -next tree, so it can be build-tested by
other people, and let's see what else is reported this week. :)
--
Gustavo
[1] https://lore.kernel.org/lkml/620ca2a5.NkAEIDEfiYoxE9%2Fu%25lkp@xxxxxxxxx/
It isn't actually an array it is a placeholder for a trailing
structure, so it is never indexed.
This is also why we hit the warning because the convient way for
userspace to compose the message is to squash the header and trailer
structs together in a super struct on the stack, then invoke the
ioctl.
Jason
