[PATCH 2/2] powerpc/perf: Fix the kernel address leak to userspace via SDAR
From: Madhavan Srinivasan <hidden>
Date: 2018-03-04 11:55:43
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
Sampled Data Address Register (SDAR) is a 64-bit register that contains the effective address of the storage operand of an instruction that was being executed, possibly out-of-order, at or around the time that the Performance Monitor alert occurred. In certain scenario SDAR happen to contain the kernel address even for userspace only sampling. Add checks to prevent it. Signed-off-by: Madhavan Srinivasan <redacted> --- arch/powerpc/perf/core-book3s.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 337db5831749..c4525323d691 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c@@ -95,7 +95,7 @@ static inline unsigned long perf_ip_adjust(struct pt_regs *regs) { return 0; } -static inline void perf_get_data_addr(struct pt_regs *regs, u64 *addrp) { } +static inline void perf_get_data_addr(struct pt_regs *regs, u64 *addrp, struct perf_event *event) { } static inline u32 perf_get_misc_flags(struct pt_regs *regs) { return 0;
@@ -174,7 +174,7 @@ static inline unsigned long perf_ip_adjust(struct pt_regs *regs) * pointed to by SIAR; this is indicated by the [POWER6_]MMCRA_SDSYNC, the * [POWER7P_]MMCRA_SDAR_VALID bit in MMCRA, or the SDAR_VALID bit in SIER. */ -static inline void perf_get_data_addr(struct pt_regs *regs, u64 *addrp) +static inline void perf_get_data_addr(struct pt_regs *regs, u64 *addrp, struct perf_event *event) { unsigned long mmcra = regs->dsisr; bool sdar_valid;
@@ -198,6 +198,11 @@ static inline void perf_get_data_addr(struct pt_regs *regs, u64 *addrp) if (!(mmcra & MMCRA_SAMPLE_ENABLE) || sdar_valid) *addrp = mfspr(SPRN_SDAR); + + if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN) && + (event->attr.exclude_kernel || event->attr.exclude_hv) && + is_kernel_addr(mfspr(SPRN_SDAR))) + *addrp = 0; } static bool regs_sihv(struct pt_regs *regs)
@@ -2054,7 +2059,7 @@ static void record_and_restart(struct perf_event *event, unsigned long val, if (event->attr.sample_type & (PERF_SAMPLE_ADDR | PERF_SAMPLE_PHYS_ADDR)) - perf_get_data_addr(regs, &data.addr); + perf_get_data_addr(regs, &data.addr, event); if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) { struct cpu_hw_events *cpuhw;
--
2.7.4