Re: [PATCH] KVM: x86: Zero reserved synic flags when delivering message to avoid stack leak

[Sean Christopherson]

On Wed, 26 Aug 2026 11:44:49 -0700, Sean Christopherson wrote:
> Ensure all reserved flags are zeroed when setting the msg_pending flag as
> part of SynIC message delivery, as setting only msg_pending can leak seven
> bits of kernel stack data to the guest.  E.g. gcc typically uses a
> bitwise-OR to set the msg_pending flag, without initializing the on-stack
> variable.
> 
> Precisely zero the flags, e.g. as opposed to zeroing the entire structure,
> to make it somewhat more obvious that the flags *need* to be zeroed.  E.g.
> it would be quite easy to misread the initial read of guest memory and
> think that zeroing the entire structure is completely superfluous.
> 
> [...]

Applied to kvm-x86 misc, thanks!

[1/1] KVM: x86: Zero reserved synic flags when delivering message to avoid stack leak
      https://github.com/kvm-x86/linux/commit/2616f497506a

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