On POWER8 systems that don't have ibm,power-rng available, a guest that ignores the KVM_CAP_PPC_HWRNG flag and calls H_RANDOM anyway will dereference a NULL pointer. And on machines with darn instead of ibm,power-rng, H_RANDOM won't work at all.

This patch kills two birds with one stone, by routing H_RANDOM calls to ppc_md.get_random_seed, and doing the real mode check inside of it.

Cc: stable@vger.kernel.org # v4.1+ Cc: Michael Ellerman mpe@ellerman.id.au Fixes: e928e9cb3601 ("KVM: PPC: Book3S HV: Add fast real-mode H_RANDOM implementation.") Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com --- arch/powerpc/include/asm/archrandom.h | 5 ---- arch/powerpc/kvm/book3s_hv_builtin.c | 7 +++--- arch/powerpc/platforms/powernv/rng.c | 33 +++++++-------------------- 3 files changed, 12 insertions(+), 33 deletions(-)

diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h index 11d4815841ab..3af27bb84a3d 100644 --- a/arch/powerpc/include/asm/archrandom.h +++ b/arch/powerpc/include/asm/archrandom.h @@ -38,12 +38,7 @@ static inline bool __must_check arch_get_random_seed_int(unsigned int *v) #endif /* CONFIG_ARCH_RANDOM */

#ifdef CONFIG_PPC_POWERNV -int pnv_hwrng_present(void); int pnv_get_random_long(unsigned long *v); -int pnv_get_random_real_mode(unsigned long *v); -#else -static inline int pnv_hwrng_present(void) { return 0; } -static inline int pnv_get_random_real_mode(unsigned long *v) { return 0; } #endif

#endif /* _ASM_POWERPC_ARCHRANDOM_H */ diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c index 799d40c2ab4f..3abaef5f9ac2 100644 --- a/arch/powerpc/kvm/book3s_hv_builtin.c +++ b/arch/powerpc/kvm/book3s_hv_builtin.c @@ -19,7 +19,7 @@ #include <asm/interrupt.h> #include <asm/kvm_ppc.h> #include <asm/kvm_book3s.h> -#include <asm/archrandom.h> +#include <asm/machdep.h> #include <asm/xics.h> #include <asm/xive.h> #include <asm/dbell.h> @@ -176,13 +176,14 @@ EXPORT_SYMBOL_GPL(kvmppc_hcall_impl_hv_realmode);

int kvmppc_hwrng_present(void) { - return pnv_hwrng_present(); + return ppc_md.get_random_seed != NULL; } EXPORT_SYMBOL_GPL(kvmppc_hwrng_present);

long kvmppc_rm_h_random(struct kvm_vcpu *vcpu) { - if (pnv_get_random_real_mode(&vcpu->arch.regs.gpr[4])) + if (ppc_md.get_random_seed && + ppc_md.get_random_seed(&vcpu->arch.regs.gpr[4])) return H_SUCCESS;

return H_HARDWARE; diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c index 386b44660e76..4a48566528c0 100644 --- a/arch/powerpc/platforms/powernv/rng.c +++ b/arch/powerpc/platforms/powernv/rng.c @@ -29,15 +29,6 @@ struct pnv_rng {

static DEFINE_PER_CPU(struct pnv_rng *, pnv_rng);

-int pnv_hwrng_present(void) -{ - struct pnv_rng *rng; - - rng = get_cpu_var(pnv_rng); - put_cpu_var(rng); - return rng != NULL; -} - static unsigned long rng_whiten(struct pnv_rng *rng, unsigned long val) { unsigned long parity; @@ -58,17 +49,6 @@ static unsigned long rng_whiten(struct pnv_rng *rng, unsigned long val) return val; }

-int pnv_get_random_real_mode(unsigned long *v) -{ - struct pnv_rng *rng; - - rng = raw_cpu_read(pnv_rng); - - *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real)); - - return 1; -} - static int pnv_get_random_darn(unsigned long *v) { unsigned long val; @@ -105,11 +85,14 @@ int pnv_get_random_long(unsigned long *v) { struct pnv_rng *rng;

- rng = get_cpu_var(pnv_rng); - - *v = rng_whiten(rng, in_be64(rng->regs)); - - put_cpu_var(rng); + if (mfmsr() & MSR_DR) { + rng = raw_cpu_read(pnv_rng); + *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real)); + } else { + rng = get_cpu_var(pnv_rng); + *v = rng_whiten(rng, in_be64(rng->regs)); + put_cpu_var(rng); + }

return 1; }