perf/x86: Check data address for IBS software filter

The IBS software filter is filtering kernel samples for regular users in
the PMI handler.  It checks the instruction address in the IBS register to
determine if it was in kernel mode or not.

But it turns out that it's possible to report a kernel data address even
if the instruction address belongs to user-space.  Matteo Rizzo
found that when an instruction raises an exception, IBS can report some
kernel data addresses like IDT while holding the faulting instruction's
RIP.  To prevent an information leak, it should double check if the data
address in PERF_SAMPLE_DATA is in the kernel space as well.

[ mingo: Clarified the changelog ]

Suggested-by: Matteo Rizzo <matteorizzo@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250317163755.1842589-1-namhyung@kernel.org

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index e7a8b8758e088f618db06fad59fb959dccc71925..c465005920029378d1923f84efefd383e9a6c6d3 100644 (file)
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -1128,8 +1128,13 @@ fail:
                regs.flags |= PERF_EFLAGS_EXACT;
        }
 
+       if (perf_ibs == &perf_ibs_op)
+               perf_ibs_parse_ld_st_data(event->attr.sample_type, &ibs_data, &data);
+
        if ((event->attr.config2 & IBS_SW_FILTER_MASK) &&
-           perf_exclude_event(event, &regs)) {
+           (perf_exclude_event(event, &regs) ||
+            ((data.sample_flags & PERF_SAMPLE_ADDR) &&
+             event->attr.exclude_kernel && kernel_ip(data.addr)))) {
                throttle = perf_event_account_interrupt(event);
                goto out;
        }
@@ -1144,9 +1149,6 @@ fail:
                perf_sample_save_raw_data(&data, event, &raw);
        }
 
-       if (perf_ibs == &perf_ibs_op)
-               perf_ibs_parse_ld_st_data(event->attr.sample_type, &ibs_data, &data);
-
        /*
         * rip recorded by IbsOpRip will not be consistent with rsp and rbp
         * recorded as part of interrupt regs. Thus we need to use rip from