On Mon, Sep 27, 2021 at 01:49:10PM +0100, Alexandru Elisei wrote: > If read_id_reg() is called for an ID register which is Read-As-Zero > (RAZ), it initializes the return value to zero, then goes through a list > of registers which require special handling. > > By not returning as soon as it tests if the register is RAZ, it creates > the opportunity for bugs, if a patch changes a register to RAZ (like has > happened with PMSWINC_EL0 in commit 11663111cd49), but doesn't remove the > special handling from read_id_reg(); or if a register is RAZ in certain > situations, and readable in others. > > Return early as to make it impossible for a RAZ register to be anything > other than zero. > > Signed-off-by: Alexandru Elisei <[email protected]> > --- > arch/arm64/kvm/sys_regs.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index 1d46e185f31e..4adda8bf3168 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -1064,7 +1064,12 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, > struct sys_reg_desc const *r, bool raz) > { > u32 id = reg_to_encoding(r); > - u64 val = raz ? 0 : read_sanitised_ftr_reg(id); > + u64 val; > + > + if (raz) > + return 0; > + > + val = read_sanitised_ftr_reg(id); > > switch (id) { > case SYS_ID_AA64PFR0_EL1: > -- > 2.33.0 > > _______________________________________________ > kvmarm mailing list > [email protected] > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm > Reviewed-by: Andrew Jones <[email protected]>
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