On 8/25/2020 2:14 AM, Florian Weimer wrote:
* Andy Lutomirski:
quoted
On Mon, Aug 24, 2020 at 5:30 PM Yu-cheng Yu [off-list ref] wrote:
quoted
From: "H.J. Lu" <redacted>
Emulation of the legacy vsyscall page is required by some programs built
before 2013. Newer programs after 2013 don't use it. Disallow vsyscall
emulation when Control-flow Enforcement (CET) is enabled to enhance
security.
NAK.
By all means disable execute emulation if CET-IBT is enabled at the
time emulation is attempted, and maybe even disable the vsyscall page
entirely if you can magically tell that CET-IBT will be enabled when a
process starts, but you don't get to just disable it outright on a
CET-enabled kernel.
Yeah, we definitely would have to revert/avoid this downstream. People
definitely want to run glibc-2.12-era workloads on current kernels.
Thanks for catching it.
That makes sense. I will update the patch.
Thanks,
Yu-cheng