From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oa1-f46.google.com (mail-oa1-f46.google.com [209.85.160.46]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 57E3933D51A for ; Tue, 6 Oct 2026 22:40:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.46 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791326411; cv=none; b=XO3AjUrpMf64dVQEk2tuO6BNzGBKknSF5V5WXgg33z2BE9FM+Lu8dSlPJSSkrVDy6GOkCp7xSGSHdQnAoel3GrmMQoq6GWrhWt7oHazP+vcVWcYeIzcDp4nFEPLrGXACfJLOFBPnEjuH7iCev6DHgB5AAinKfpXId78o3DaOyjA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791326411; c=relaxed/simple; bh=hPOUmV/xGE5eS0kZpd5MJCVPYwrNotNiv1TTrk+TckI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=bamR7VQifGHOU+SwWmmv7F1GmCxZGAU4Cp18tGl8CMr3R8b9yy/4DEDDT3CCg7p+XsaVmTNsuL9Zfhs1fKfvJTbrwD070Pkeczf3sE/DfA3jewzeiKwDLkFCxUPHuTReVUNRW1NFCsnihnDaIMFJKSewRkWiLu2VgBo/S5t8J4w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=openai.com; spf=pass smtp.mailfrom=openai.com; dkim=pass (1024-bit key) header.d=openai.com header.i=@openai.com header.b=AJx39qsk; arc=none smtp.client-ip=209.85.160.46 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=openai.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=openai.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=openai.com header.i=@openai.com header.b="AJx39qsk" Received: by mail-oa1-f46.google.com with SMTP id 586e51a60fabf-455ca262ccbso858278fac.1 for ; Tue, 06 Oct 2026 15:40:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=openai.com; s=google; t=1791326409; x=1791931209; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to:content-type; bh=bMDhGYH4rM/hZGPUiF2V3RD2josdEfJ5uDI1Xaf78dg=; b=AJx39qskExIGcEEPyA1S7gUovLD1/9lvzGRuxxNGEQCvkP4boMxmhU/DcwqJkX9NGD J3WVyGeqh3EBpMLNczl6mJFHsel61um7gppKrwGleCcaRLWgkfZBpG4mMPrfd5dfeB/V yBzuutgPa9qLtUR2P7Nm0bCr+H5dOEucSLzCo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791326409; x=1791931209; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=bMDhGYH4rM/hZGPUiF2V3RD2josdEfJ5uDI1Xaf78dg=; b=v1qRqiytO+M5M20dZgB/kSbuknrwP0FBQJzORFEpD/clPNxx+wvchlJxr3vu8Ldb2Y ZcNLVhZAF9miBEMTQeV4gcYILVtrERXmNK2CvCfVALslYST9eUUCV/IlDUzafex53XD7 n5VVZsBRV3xDkQAbYwsCfIi7wfQuX4kbj4NutZBGKzD3NBAT5iZcQQI73I+lJ1kjcTMm UZDOF5O040vIhmGosGJLljn05jgefpxy3GJ1u38GrT2w3c6Z4V95BWDFUJxW7dn0c+U4 wOS3pMknMYfq8vwSd7lplv1HG9wV/Pg2YrIRm9fGV90U3Y4nEnuubOnB0DHPWcCS1Q6j Lb8Q== X-Gm-Message-State: AFuF++mkOLyoz4MeXoiQnd+dZVSZvHLfgmcdPQHk7kBH3UuIeg2k/D6Z w3jubuaZjJde2lcBBrLlLepL0wAPXAzRFRjsjBlPGisnEYrnMJ83tSJ3cRtaSQCZ1mg= X-Gm-Gg: AYBFou00EEWUmqyLLh0RMtEIJy0/qR4eTS2XejQgQCIaLv2LEyDwttccdTU1+SmXXcK eQ1roEUFZjVTTrj+kssUip1u58T1gTOFZs9FjXOAuALUz+7xCTQ45Dt1Y2bn62zos1yE3FzyrmS dYmxgaShwk2FqxjKd3aCyoAMz9YL3XTB7BL+//to117h+xEzPWgSP/b4Y87/GJ/6vpLyAxfxKX6 v0abv2wYIyJ7tQiQ/xqGRtBViHa50hjFNGeI7hyjdbZswRs/KD8aql8qrafCQ3u+wiQZGXaxEeN 1emZT/bOOMW0DJmK1awkr97hSsmMzmeKP17ej8bXBbr9zmeVEpzZHzPIJjC3Y8lbtvC1Mcxg1PM N4XdTlA7zhXsZv2ijRUL2IEKFudrDeawPiE3d3wJg4rvXgEaNGCjeB/zUcq5FWIPKBfqwrQAiu1 MzCWlEt7B7P1uslFUGGa7GUE5tX201K++TYTsuDKR/Pwi8yKPqpnpOA8hR9s4hXiHLRPkE0i5dg 6/emXMnXJ+Bq6D+cNIAXwoteP1fKxcK15c62TneiyIoQHueD8YtoC5/SoJd239rRJ9vaVo/peM= X-Received: by 2002:a05:6870:6128:b0:494:b0db:4e0d with SMTP id 586e51a60fabf-4a259148369mr477880fac.7.1791326409160; Tue, 06 Oct 2026 15:40:09 -0700 (PDT) Received: from com-75606.corp.openai.org ([199.47.143.7]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-4a25701702esm689475fac.6.2026.10.06.15.40.08 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 06 Oct 2026 15:40:08 -0700 (PDT) From: Kyle Zeng To: linux-trace-kernel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, outbounddisclosures@openai.com, Kyle Zeng Subject: [PATCH] tracing: Restrict perf filters that read kernel strings Date: Tue, 6 Oct 2026 15:40:05 -0700 Message-ID: <20261006224005.49636-1-kylebot@openai.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A task-bound, counting-only syscall tracepoint can be opened without permission to read raw kernel tracepoint data. Setting exclude_kernel does not prevent its filter from running: perf_syscall_enter() submits the saved user-mode registers. Pointer-string filters use FILTER_PRED_FN_PCHAR by default, which reads through strncpy_from_kernel_nofault(). For sys_enter_openat, for example, the filename field comes directly from a syscall argument. An unprivileged caller can pass a kernel address, install a filter such as 'filename ~ "Linux version*"', and use the event count to test the contents of kernel memory, even with perf_event_paranoid=2. Check the compiled filter before installing it and require the same kernel and raw-tracepoint permissions as access to raw kernel tracepoint data for FILTER_PRED_FN_PCHAR. Inspect every predicate so that other events, operators, and boolean expressions cannot bypass the check. Return the permission error through the existing cleanup path before publishing the filter. Keep user-pointer (.ustring) and record-local predicates available under the existing policy. This leaves tracefs filtering and authorized kernel string filtering unchanged. Fixes: 5967bd5c4239 ("tracing: Let filter_assign_type() detect FILTER_PTR_STRING") Assisted-by: Codex:gpt-6-astra Signed-off-by: Kyle Zeng --- kernel/trace/trace_events_filter.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 2b46ca536045..76aca560491b 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -2704,6 +2704,28 @@ static int ftrace_function_set_filter(struct perf_event *event, } #endif /* CONFIG_FUNCTION_TRACER */ +static int ftrace_profile_filter_perm(struct event_filter *filter) +{ + struct prog_entry *prog = rcu_dereference_protected(filter->prog, + lockdep_is_held(&event_mutex)); + int i, err; + + for (i = 0; prog[i].pred; i++) { + if (prog[i].pred->fn_num != FILTER_PRED_FN_PCHAR) + continue; + + /* + * Even a counting filter can reveal kernel string data. + * Require the same access as raw kernel tracepoints. + */ + err = perf_allow_kernel(); + if (err) + return err; + return perf_allow_tracepoint(); + } + return 0; +} + int ftrace_profile_set_filter(struct perf_event *event, int event_id, char *filter_str) { @@ -2725,6 +2747,10 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id, if (err) goto free_filter; + err = ftrace_profile_filter_perm(filter); + if (err) + goto free_filter; + if (ftrace_event_is_function(call)) err = ftrace_function_set_filter(event, filter); else base-commit: fd179f8a05be3ccae366b9b96e176b51fbe54aab -- 2.53.0