Re: [PATCH -next] KVM: arm64: Fix possible null-ptr-deref in idregs_debug_show

[Marc Zyngier <maz@kernel.org>]

On Thu, 24 Oct 2024 09:33:50 +0100,
Gaosheng Cui <cuigaosheng1@huawei.com> wrote:
> 
> The idregs_debug_show() maybe return nullptr, we need to check desc
> before dereference it to avoid possible null pointer dereferences.
> 
> Fixes: 410db103f6eb ("KVM: arm64: Make idregs debugfs iterator search sysreg table directly")
> Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
> ---
>  arch/arm64/kvm/sys_regs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index ff8c4e1b847e..b1c59773b9c0 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -4135,7 +4135,7 @@ static int idregs_debug_show(struct seq_file *s, void *v)
>  
>  	desc = idregs_debug_find(kvm, kvm->arch.idreg_debugfs_iter);
>  
> -	if (!desc->name)
> +	if (!desc || !desc->name)
>  		return 0;
>  
>  	seq_printf(s, "%20s:\t%016llx\n",

Can you show a case where this happens in practice?

The check for NULL is already in idregs_debug_next(), and I don't see
how this can actually be triggered.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.