From 83fb2a49cc19436838c4b7ad0b939f52ffddc11d Mon Sep 17 00:00:00 2001 From: Madhavan Srinivasan Date: Wed, 21 Mar 2018 17:10:25 +0530 Subject: [PATCH] powerpc/perf: Prevent kernel address leak to userspace via BHRB buffer [ Upstream commit bb19af816025d495376bd76bf6fbcf4244f9a06d ] The current Branch History Rolling Buffer (BHRB) code does not check for any privilege levels before updating the data from BHRB. This could leak kernel addresses to userspace even when profiling only with userspace privileges. Add proper checks to prevent it. Acked-by: Balbir Singh Signed-off-by: Madhavan Srinivasan Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/perf/core-book3s.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c index 4eba7c00ea1f..02b9c9914b09 100644 --- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -448,6 +448,16 @@ static void power_pmu_bhrb_read(struct cpu_hw_events *cpuhw) /* invalid entry */ continue; + /* + * BHRB rolling buffer could very much contain the kernel + * addresses at this point. Check the privileges before + * exporting it to userspace (avoid exposure of regions + * where we could have speculative execution) + */ + if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN) && + is_kernel_addr(addr)) + continue; + /* Branches are read most recent first (ie. mfbhrb 0 is * the most recent branch). * There are two types of valid entries: