Re: [PATCH v2 1/3] Fix userfaultfd_api to return EINVAL as expected

On Sun, 23 Jun 2024 11:26:37 -0400 Peter Xu peterx@redhat.com wrote:

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Fixes: e06f1e1dd499 ("userfaultfd: wp: enabled write protection in userfaultfd API")

A userspace-triggerable WARN is bad. I added cc:stable to this.

Andrew,

Note that this change may fix a WARN, but it may also start to break userspace which might be worse if it happens, IMHO. I forgot to mention that here, but only mentioned that in v1, and from that POV not copying stable seems the right thing.

https://lore.kernel.org/all/ZjuIEH8TW2tWcqXQ@x1n/

    In summary: I think we can stick with Fixes on e06f1e1dd499, but we
    don't copy stable.  The major reason we don't copy stable here is
    not only about complexity of such backport, but also that there can
    be apps trying to pass in unsupported bits (even if the kernel
    didn't support it) but keep using MISSING mode only, then we
    shouldn't fail them easily after a stable upgrade.  Just smells
    dangerous to backport.

OK. And I'll move it into the 6.11-rc1 queue, for the next merge window.