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authorMichael Ellerman <mpe@ellerman.id.au>2022-07-28 00:32:17 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2022-07-28 16:22:15 +1000
commit90b5d4fe0b3ba7f589c6723c6bfb559d9e83956a (patch)
treefd415104a208db7f82c02386962ae6589b36c626 /arch/powerpc
parentcd1e64935f79e31d666172c52c951ca97152b783 (diff)
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 <Jason@zx2c4.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20220727143219.2684192-1-mpe@ellerman.id.au
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/platforms/powernv/rng.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
index 3805ad13b8f3..2287c9cd0cd5 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));