From: Ravi Bangoria Date: Mon, 16 Feb 2026 04:22:15 +0000 (+0000) Subject: perf/amd/ibs: Avoid calling perf_allow_kernel() from the IBS NMI handler X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b0a09142622a994c4f4088c3f61db5da87cfc711;p=thirdparty%2Fkernel%2Flinux.git perf/amd/ibs: Avoid calling perf_allow_kernel() from the IBS NMI handler Calling perf_allow_kernel() from the NMI context is unsafe and could be fatal. Capture the permission at event-initialization time by storing it in event->hw.flags, and have the NMI handler rely on that cached flag instead of making the call directly. Fixes: 50a53b60e141d ("perf/amd/ibs: Prevent leaking sensitive data to userspace") Reported-by: Sadasivan Shaiju Signed-off-by: Ravi Bangoria Signed-off-by: Peter Zijlstra (Intel) Acked-by: Namhyung Kim Link: https://patch.msgid.link/20260216042216.1440-5-ravi.bangoria@amd.com --- diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c index 05b7c9f2ec338..004226b52ac79 100644 --- a/arch/x86/events/amd/ibs.c +++ b/arch/x86/events/amd/ibs.c @@ -313,6 +313,9 @@ static int perf_ibs_init(struct perf_event *event) if (ret) return ret; + if (perf_allow_kernel()) + hwc->flags |= PERF_X86_EVENT_UNPRIVILEGED; + if (hwc->sample_period) { if (config & perf_ibs->cnt_mask) /* raw max_cnt may not be set */ @@ -1349,7 +1352,7 @@ fail: * unprivileged users. */ if ((event->attr.sample_type & PERF_SAMPLE_RAW) && - perf_allow_kernel()) { + (hwc->flags & PERF_X86_EVENT_UNPRIVILEGED)) { perf_ibs_phyaddr_clear(perf_ibs, &ibs_data); } diff --git a/arch/x86/events/perf_event_flags.h b/arch/x86/events/perf_event_flags.h index 70078334e4a33..47f84ee8f5409 100644 --- a/arch/x86/events/perf_event_flags.h +++ b/arch/x86/events/perf_event_flags.h @@ -23,3 +23,4 @@ PERF_ARCH(PEBS_LAT_HYBRID, 0x0020000) /* ld and st lat for hybrid */ PERF_ARCH(NEEDS_BRANCH_STACK, 0x0040000) /* require branch stack setup */ PERF_ARCH(BRANCH_COUNTERS, 0x0080000) /* logs the counters in the extra space of each branch */ PERF_ARCH(ACR, 0x0100000) /* Auto counter reload */ +PERF_ARCH(UNPRIVILEGED, 0x0200000) /* Unprivileged event (wrt perf_allow_kernel()) */