linux-kernel - Re: [PATCH MANUALSEL 5.10 4/4] KVM: downgrade two BUG_ONs to WARN_ON

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Date:   Mon, 13 Dec 2021 15:22:07 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc:     kvm@...r.kernel.org
Subject: Re: [PATCH MANUALSEL 5.10 4/4] KVM: downgrade two BUG_ONs to
 WARN_ON_ONCE

On 12/13/21 15:20, Sasha Levin wrote:
> From: Paolo Bonzini <pbonzini@...hat.com>
> 
> [ Upstream commit 5f25e71e311478f9bb0a8ef49e7d8b95316491d7 ]
> 
> This is not an unrecoverable situation.  Users of kvm_read_guest_offset_cached
> and kvm_write_guest_offset_cached must expect the read/write to fail, and
> therefore it is possible to just return early with an error value.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>   virt/kvm/kvm_main.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 97ac3c6fd4441..4a7d377b3a500 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2590,7 +2590,8 @@ int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
>   	int r;
>   	gpa_t gpa = ghc->gpa + offset;
>   
> -	BUG_ON(len + offset > ghc->len);
> +	if (WARN_ON_ONCE(len + offset > ghc->len))
> +		return -EINVAL;
>   
>   	if (slots->generation != ghc->generation) {
>   		if (__kvm_gfn_to_hva_cache_init(slots, ghc, ghc->gpa, ghc->len))
> @@ -2627,7 +2628,8 @@ int kvm_read_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
>   	int r;
>   	gpa_t gpa = ghc->gpa + offset;
>   
> -	BUG_ON(len + offset > ghc->len);
> +	if (WARN_ON_ONCE(len + offset > ghc->len))
> +		return -EINVAL;
>   
>   	if (slots->generation != ghc->generation) {
>   		if (__kvm_gfn_to_hva_cache_init(slots, ghc, ghc->gpa, ghc->len))
> 

Acked-by: Paolo Bonzini <pbonzini@...hat.com>