From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f50.google.com (mail-ej1-f50.google.com [209.85.218.50]) (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 1735F2F9DB5 for ; Tue, 16 Sep 2025 21:52:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.50 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758059539; cv=none; b=pAmZFwGiCDeoxNsQQYJ5feDaynaqYy0NrGQYmdlFtn+kIhN0CG/gi41tc/Bdkj4eTWt6ATKSIttjlwD8a0uVWnRPVp82ThtpN8+8+1isIGKw8J1MjPzMAzpjazmVYhe8wZAuda86Xy34OjfC8rkvvPPwBDXb0mMyjv7KS/+vX/k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758059539; c=relaxed/simple; bh=I7vgzpb4iQRotjVoiX/pLxoru+xY5k4ZR4ZCWGtLhqk=; h=From:Date:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QFDIU+E50or0vJKfYKYWk/M+tgL7bc3Jo/Kor7PlYGYKsVUHjkHnBJ/fhgJOJeK0+ckxRcrMJ/FhPYazQw18sazZA43qA/kfKGWmoqPf/bgTERHQWXdGWE8ZE9z01WUxzgjTIqHeJxSKSvXPmoP39sbsHD/OPNMH2zvDGOoreKs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=T5EvIdYK; arc=none smtp.client-ip=209.85.218.50 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="T5EvIdYK" Received: by mail-ej1-f50.google.com with SMTP id a640c23a62f3a-b04ba3de760so753627866b.0 for ; Tue, 16 Sep 2025 14:52:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1758059535; x=1758664335; darn=vger.kernel.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:date:from:from:to :cc:subject:date:message-id:reply-to; bh=HmHjJhcmqy1sBBEmVO7MB7cGRMGtnkst9/nnRmc5EGM=; b=T5EvIdYKM7xdM80hgROGpZCjWUgiJyj6DNTUADzcCLD4yLYcqmtXVTmvW3+7fpwF49 /1RkICJtwQU2llZPTyAbZVkHRQ8uBP9DR6mL1qO10ss66D6YTTDTN7wGITa2Rhtvk2r7 RK4hPqbl5KImlcQaDGEzLjpKVuhnM8ds/63Bbl0leLu8GWKGf/JQStWel3qZvP/RXvEk MGjP21F4XJiTJNFGacNlozYeVZqnyj5Hmn2FWTvfY/BiIPG/rcoMu7LtNXq4jQH9k0rs wclDdfnjRr9VItIOY3f1gv66UroRHmbwr4G+V6FYmuq02IftQEapEmpaVQ3GbMFYtYAg tqKg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1758059535; x=1758664335; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:date:from :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=HmHjJhcmqy1sBBEmVO7MB7cGRMGtnkst9/nnRmc5EGM=; b=e2Pgun4K8pIWl2KbQ7x1vTO8WmMFMyia3sBVR+P2d75iZGKjkVlAQs67GLsr1zOegd o5D44uaxstKxgC18ajPYONnQTBlkCeWTqlEgHm41dIqEnOKJnLn+S/gzWDShZTtFpOat F/jyIrEQW8WVazPeqMGhxWYUryvMzYQBCldCIOGPLUP1DK/n0u8KPZ3YUC1O4DE0CUa5 ttPdii7S+EVfIYM37tGbVMFmMxSUSpVm5IvpLG9MiQGYCNoAYHmrAJwtVX9YY28LPSi/ 5EUbGTkvQnVC+ocqhGqjS+D7dIxvKP+0+CURmsTDdgKz7Y6QHHRyt7gdmL6uPcQYQDKk sd5Q== X-Forwarded-Encrypted: i=1; AJvYcCWSZvj4xcpHX/gLMM8AqMwLK/NtWWrcSjVCQiAeksvubJGE35hq23RHqsy0zBUIGPeeFEAMIlOoMXpGJIKSqydF85k=@vger.kernel.org X-Gm-Message-State: AOJu0YxlR6/gDLDGyBebqE4Oc1U0J+Mvkk4jNNywipH3vfq7rPoyqAoi CfsC3eV1LgvWuOr4q6nDWWjyjw4coYg2j2uVzgqJ3KrhKe3ZttIGkjNw X-Gm-Gg: ASbGncsC7dnwWarNfmVtPGLgr4iz1FY2Z+tRLJKpAmVMmU/36IGaXzd2KvSkEyeVbZo 8BmUIj+MS0NEZ/pSb12jTPm7hWluqeWSohwdSyQNPRYrTld4gLQa9UtGmpobDovztH3CFsRIsYv Kd0A5XaAe2OaZG5iuHOKaGrxqJbjPq/2vDMnkHMinbGXeuEuA5tj258I9RFCTAE/8kZWrWEU63a 35A85IZn9hrWgzpt2AaacpoqrRZbDPDiy+WiHQjfiHaWrtU7CH3btwyNO4RTiglr18aCdqFoMZy WdCWh+0cH8oa92S/V8fVLb1EIF9S8AFws6xnSXFbx5ZcarG82lq6gT0H7zAlskGB8VRVMWdQRSE /KlqvkIU8xUxYWj4mByjSFm/O5Zzy2VYXC75OdFQ= X-Google-Smtp-Source: AGHT+IEEPGcRJK3rkvIfHaTSzEc1f2K/e0Z2Jggqlv4rhtrevVG/kWh6oUJyYLTrD+W1XABPwN8FRQ== X-Received: by 2002:a17:906:dc89:b0:b12:3f5f:603b with SMTP id a640c23a62f3a-b1bb08685eamr3355066b.3.1758059535004; Tue, 16 Sep 2025 14:52:15 -0700 (PDT) Received: from krava (89-40-234-69.wdsl.neomedia.it. [89.40.234.69]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b07c6110c27sm1027530466b.66.2025.09.16.14.52.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Sep 2025 14:52:14 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 16 Sep 2025 23:52:11 +0200 To: Andrii Nakryiko Cc: Oleg Nesterov , Masami Hiramatsu , Peter Zijlstra , Andrii Nakryiko , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org, Song Liu , Yonghong Song , John Fastabend , Hao Luo , Steven Rostedt , Ingo Molnar Subject: Re: [PATCHv3 perf/core 1/6] bpf: Allow uprobe program to change context registers Message-ID: References: <20250909123857.315599-1-jolsa@kernel.org> <20250909123857.315599-2-jolsa@kernel.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Sep 09, 2025 at 12:41:36PM -0400, Andrii Nakryiko wrote: > On Tue, Sep 9, 2025 at 8:39 AM Jiri Olsa wrote: > > > > Currently uprobe (BPF_PROG_TYPE_KPROBE) program can't write to the > > context registers data. While this makes sense for kprobe attachments, > > for uprobe attachment it might make sense to be able to change user > > space registers to alter application execution. > > > > Since uprobe and kprobe programs share the same type (BPF_PROG_TYPE_KPROBE), > > we can't deny write access to context during the program load. We need > > to check on it during program attachment to see if it's going to be > > kprobe or uprobe. > > > > Storing the program's write attempt to context and checking on it > > during the attachment. > > > > Signed-off-by: Jiri Olsa > > --- > > include/linux/bpf.h | 1 + > > kernel/events/core.c | 4 ++++ > > kernel/trace/bpf_trace.c | 7 +++++-- > > 3 files changed, 10 insertions(+), 2 deletions(-) > > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > > index cc700925b802..404a30cde84e 100644 > > --- a/include/linux/bpf.h > > +++ b/include/linux/bpf.h > > @@ -1619,6 +1619,7 @@ struct bpf_prog_aux { > > bool priv_stack_requested; > > bool changes_pkt_data; > > bool might_sleep; > > + bool kprobe_write_ctx; > > u64 prog_array_member_cnt; /* counts how many times as member of prog_array */ > > struct mutex ext_mutex; /* mutex for is_extended and prog_array_member_cnt */ > > struct bpf_arena *arena; > > diff --git a/kernel/events/core.c b/kernel/events/core.c > > index 28de3baff792..c3f37b266fc4 100644 > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -11238,6 +11238,10 @@ static int __perf_event_set_bpf_prog(struct perf_event *event, > > if (prog->kprobe_override && !is_kprobe) > > return -EINVAL; > > > > + /* Writing to context allowed only for uprobes. */ > > + if (prog->aux->kprobe_write_ctx && !is_uprobe) > > + return -EINVAL; > > + > > if (is_tracepoint || is_syscall_tp) { > > int off = trace_event_get_offsets(event->tp_event); > > > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > > index 3ae52978cae6..dfb19e773afa 100644 > > --- a/kernel/trace/bpf_trace.c > > +++ b/kernel/trace/bpf_trace.c > > @@ -1521,8 +1521,6 @@ static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type > > { > > if (off < 0 || off >= sizeof(struct pt_regs)) > > return false; > > - if (type != BPF_READ) > > - return false; > > if (off % size != 0) > > return false; > > /* > > @@ -1532,6 +1530,7 @@ static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type > > if (off + size > sizeof(struct pt_regs)) > > return false; > > > > + prog->aux->kprobe_write_ctx |= type == BPF_WRITE; > > nit: minor preference for > > if (type == BPF_WRITE) > prog->aux->kprobe_write_ctx = true; ok, will change jirka > > > > return true; > > } > > > > @@ -2913,6 +2912,10 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr > > if (!is_kprobe_multi(prog)) > > return -EINVAL; > > > > + /* Writing to context is not allowed for kprobes. */ > > + if (prog->aux->kprobe_write_ctx) > > + return -EINVAL; > > + > > flags = attr->link_create.kprobe_multi.flags; > > if (flags & ~BPF_F_KPROBE_MULTI_RETURN) > > return -EINVAL; > > -- > > 2.51.0 > >