lkml.org 
[lkml]   [2022]   [Jun]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH][next] treewide: uapi: Replace zero-length arrays with flexible-array members
    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@intel.com/

    >
    > 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

    \
     
     \ /
      Last update: 2022-06-28 15:59    [W:2.754 / U:0.188 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site