From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3F3D61A58C for ; Mon, 16 Oct 2023 09:04:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="oYpkLjpM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B16F0C433C7; Mon, 16 Oct 2023 09:04:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1697447074; bh=gmDUHPu0o+gJ9pYJ29BYIYbS2jCLRprr590FQqSWCP0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oYpkLjpMZdUUEuDGFL7p5ZNlxNJwwqIMfFVP2IvElaC6z2aVBAi/FttLzQkDlgtHE ZY3SUwGLLpv1tOidh4pQBPsLo7G+8nQvWxcllpi7X2CDMRdAgNJF5Hmno+QBtfgzhf nrlG7ZPwFGI+iE4BSjyPDkbBEF7AMRTRjwDNEjcs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alexei Starovoitov , JP Kobryn , Ingo Molnar Subject: [PATCH 6.1 096/131] perf/x86/lbr: Filter vsyscall addresses Date: Mon, 16 Oct 2023 10:41:19 +0200 Message-ID: <20231016084002.450509933@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231016084000.050926073@linuxfoundation.org> References: <20231016084000.050926073@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: JP Kobryn commit e53899771a02f798d436655efbd9d4b46c0f9265 upstream. We found that a panic can occur when a vsyscall is made while LBR sampling is active. If the vsyscall is interrupted (NMI) for perf sampling, this call sequence can occur (most recent at top): __insn_get_emulate_prefix() insn_get_emulate_prefix() insn_get_prefixes() insn_get_opcode() decode_branch_type() get_branch_type() intel_pmu_lbr_filter() intel_pmu_handle_irq() perf_event_nmi_handler() Within __insn_get_emulate_prefix() at frame 0, a macro is called: peek_nbyte_next(insn_byte_t, insn, i) Within this macro, this dereference occurs: (insn)->next_byte Inspecting registers at this point, the value of the next_byte field is the address of the vsyscall made, for example the location of the vsyscall version of gettimeofday() at 0xffffffffff600000. The access to an address in the vsyscall region will trigger an oops due to an unhandled page fault. To fix the bug, filtering for vsyscalls can be done when determining the branch type. This patch will return a "none" branch if a kernel address if found to lie in the vsyscall region. Suggested-by: Alexei Starovoitov Signed-off-by: JP Kobryn Signed-off-by: Ingo Molnar Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- arch/x86/events/utils.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/arch/x86/events/utils.c +++ b/arch/x86/events/utils.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include +#include #include "perf_event.h" @@ -132,9 +133,9 @@ static int get_branch_type(unsigned long * The LBR logs any address in the IP, even if the IP just * faulted. This means userspace can control the from address. * Ensure we don't blindly read any address by validating it is - * a known text address. + * a known text address and not a vsyscall address. */ - if (kernel_text_address(from)) { + if (kernel_text_address(from) && !in_gate_area_no_mm(from)) { addr = (void *)from; /* * Assume we can get the maximum possible size