This is a note to let you know that I've just added the patch titled powerpc/powernv: Avoid crashing if rng is NULL to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: powerpc-powernv-avoid-crashing-if-rng-is-null.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 90b5d4fe0b3ba7f589c6723c6bfb559d9e83956a Mon Sep 17 00:00:00 2001 From: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Date: Thu, 28 Jul 2022 00:32:17 +1000 Subject: powerpc/powernv: Avoid crashing if rng is NULL From: Michael Ellerman <mpe@xxxxxxxxxxxxxx> commit 90b5d4fe0b3ba7f589c6723c6bfb559d9e83956a upstream. 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@xxxxxxxxxxxxxxx # v4.1+ Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220727143219.2684192-1-mpe@xxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/powerpc/platforms/powernv/rng.c | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/powerpc/platforms/powernv/rng.c +++ b/arch/powerpc/platforms/powernv/rng.c @@ -63,6 +63,8 @@ int powernv_get_random_real_mode(unsigne struct powernv_rng *rng; rng = raw_cpu_read(powernv_rng); + if (!rng) + return 0; *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real)); Patches currently in stable-queue which might be from mpe@xxxxxxxxxxxxxx are queue-4.14/macintosh-adb-fix-oob-read-in-do_adb_query-function.patch queue-4.14/powerpc-powernv-avoid-crashing-if-rng-is-null.patch queue-4.14/powerpc-fsl-pci-fix-class-code-of-pcie-root-port.patch