fix(macos): allow reading kern.hv_vmm_present sysctl#312
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Chromium-based browsers PCHECK sysctlbyname("kern.hv_vmm_present") in
base::IsVirtualMachine() during startup (base/mac/mac_util.mm). When the
seatbelt profile denies this sysctl, the browser aborts with a FATAL at
mac_util.mm before launching, which breaks allowBrowserProcess support
for any modern Chrome/Chromium.
Add kern.hv_vmm_present to the sysctl-read allowlist so browsers can
start under the sandbox. It is a read-only, single-bit value (VM/host)
and is strictly less sensitive than entries already allowed (e.g.
kern.bootargs, kern.hostname).
Add a regression test asserting the sysctl is readable under the profile.
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I'm running a rails project with cabybara specs, using Selenium and chromedriver. Chrome/Chromium were not able to run without these changes. To be honest, I don't know much about the subject, but the agent help me fixed it. Let me know if that makes sense to the project.
Agent's description below.
Scenario
Running a Rails app's Capybara feature specs (Selenium + headless Chrome via chromedriver) with the bash command wrapped by the seatbelt sandbox (allowBrowserProcess: true). Chrome launched but every test died at visit with session not created: Chrome instance exited / tab crashed.
Root cause
Modern Chromium-based browsers PCHECK sysctlbyname("kern.hv_vmm_present") inside base::IsVirtualMachine() during startup (base/mac/mac_util.mm). The seatbelt profile didn't allow that sysctl, so the check failed and Chrome aborted with a FATAL before the renderer ever came up:
This effectively breaks allowBrowserProcess for any current Chrome/Chromium on macOS.
Fix
Add kern.hv_vmm_present to the sysctl-read allowlist. It's a read-only, single-bit value (running under a VM or not) and is strictly less sensitive than entries already permitted (kern.bootargs, kern.hostname, etc.), so there's no meaningful security trade-off.
Testing