From: Michael Ellerman Date: Wed, 27 Jul 2022 14:32:17 +0000 (+1000) Subject: powerpc/powernv: Avoid crashing if rng is NULL X-Git-Tag: v6.6.17~6858^2~14 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=90b5d4fe0b3ba7f589c6723c6bfb559d9e83956a;p=platform%2Fkernel%2Flinux-rpi.git powerpc/powernv: Avoid crashing if rng is NULL On a bare-metal Power8 system that doesn't have an "ibm,power-rng", a malicious QEMU and guest that ignore the absence of the KVM_CAP_PPC_HWRNG flag, and calls H_RANDOM anyway, will dereference a NULL pointer. In practice all Power8 machines have an "ibm,power-rng", but let's not rely on that, add a NULL check and early return in powernv_get_random_real_mode(). Fixes: e928e9cb3601 ("KVM: PPC: Book3S HV: Add fast real-mode H_RANDOM implementation.") Cc: stable@vger.kernel.org # v4.1+ Signed-off-by: Jason A. Donenfeld Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220727143219.2684192-1-mpe@ellerman.id.au --- diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c index 3805ad1..2287c9c 100644 --- a/arch/powerpc/platforms/powernv/rng.c +++ b/arch/powerpc/platforms/powernv/rng.c @@ -63,6 +63,8 @@ int powernv_get_random_real_mode(unsigned long *v) struct powernv_rng *rng; rng = raw_cpu_read(powernv_rng); + if (!rng) + return 0; *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real));