From: Sandipan Das Date: Fri, 10 Jul 2026 10:45:27 +0000 (+0530) Subject: perf/x86/amd/lbr: Fix kernel address leakage X-Git-Tag: v7.2-rc3~12^2~1 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2a892294b83f541115c94b0bb637f39bef187657;p=thirdparty%2Fkernel%2Flinux.git perf/x86/amd/lbr: Fix kernel address leakage A user-only branch stack can contain branches that originate from the kernel. As a result, kernel addresses are exposed to user space even when PERF_SAMPLE_BRANCH_USER is requested. On AMD processors supporting X86_FEATURE_AMD_LBR_V2, perf can still report SYSRET/ERET entries for which the branch-from addresses are in the kernel. E.g. $ perf record -e cycles -o - -j any,save_type,u -- \ perf bench syscall basic --loop 1000 | \ perf script -i - -F brstack|tr ' ' '\n'| \ grep -E '0x[89a-f][0-9a-f]{15}' ... 0xffffffff81001268/0x717a90a38f1a/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a90a39157/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a90a2c628/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a90a41b60/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a90a260db/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a90a260db/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a8bef1c30/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH 0xffffffff81001268/0x717a8e4d3c90/M/-/-/0/ERET/NON_SPEC_CORRECT_PATH ... The reason is that the hardware filter only considers the privilege level applicable to the branch target. Extend software filtering to also validate the branch-from addresses against br_sel, so that any branch record whose branch-from address is in the kernel is dropped when PERF_SAMPLE_BRANCH_USER is requested. Fixes: f4f925dae741 ("perf/x86/amd/lbr: Add LbrExtV2 hardware branch filter support") Reported-by: Ian Rogers Signed-off-by: Sandipan Das Signed-off-by: Ingo Molnar Cc: stable@vger.kernel.org Cc: Peter Zijlstra Link: https://patch.msgid.link/a898a29725f6b2f30518354cdc2e432db66c43cf.1783680119.git.sandipan.das@amd.com --- diff --git a/arch/x86/events/amd/lbr.c b/arch/x86/events/amd/lbr.c index 5b437dc8e4ce..9d9c961989d5 100644 --- a/arch/x86/events/amd/lbr.c +++ b/arch/x86/events/amd/lbr.c @@ -127,7 +127,8 @@ static void amd_pmu_lbr_filter(void) } /* If type does not correspond, then discard */ - if (type == X86_BR_NONE || (br_sel & type) != type) { + if (type == X86_BR_NONE || (br_sel & type) != type || + (!(br_sel & X86_BR_KERNEL) && kernel_ip(cpuc->lbr_entries[i].from))) { cpuc->lbr_entries[i].from = 0; /* mark invalid */ compress = true; }