On Fri, Jun 28, 2024 at 1:58 AM Jonathan Corbet [off-list ref] wrote:

KP Singh [off-list ref] writes:

quoted

LSM hooks are currently invoked from a linked list as indirect calls
which are invoked using retpolines as a mitigation for speculative
attacks (Branch History / Target injection) and add extra overhead which
is especially bad in kernel hot paths:

I hate to bug you with a changelog nit, but this is the sort of thing
that might save others some work..

[...]

quoted

A static key guards whether an LSM static call is enabled or not,
without this static key, for LSM hooks that return an int, the presence
of the hook that returns a default value can create side-effects which
has resulted in bugs [1].

I looked in vain for [1] to see what these bugs were.  After sufficient
digging, I found that the relevant URL:

  https://lore.kernel.org/linux-security-module/20220609234601.2026362-1-kpsingh@kernel.org/ (local)

Thank you so much Jon, appreciate the attention to detail, I have
fixed it in v13.

- KP

was evidently dropped in v4 of the patch set last September, and nobody
evidently noticed.  If there's a v13, I might humbly suggest putting it
back :)

Thanks,

jon