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 64AAC2C190; Tue, 5 Nov 2024 16:31:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730824272; cv=none; b=dYYQe9lhSmV/HoyN5DMZ8YG3LoBRNUNCvCAT128I/tZ7HTYtFadk0p8mLNGxscS6wK9Jx3HKYLTMuF7t04/eO3dRIyIdbXjMQqo9IzJB4zAGZ01PST3HxKUP3pI4nsPe8B+IfgCj4Ch3MSDYI3rKUBBIx+Dertqw376X3cTAXeE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730824272; c=relaxed/simple; bh=7MOh4GwiFOvb9bVlArzUPENHDHkefPz5N7SZii2P0Hc=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=CX/LTbQDbpi/WQ5sUpV1ixJyxPJCJT48LLDweQpkThVzuXWT1ixmtc0k1+N3U+nfv+9KNj8tcCZOg6aoqDhRGVjuW/55DkQoXPBhma1d3hLi+9z4UWRh54F7yG303CegkaukEX/cyyKEs+kdFbkskTcbtX+BX59hhPEb/+BLtNc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 910B2C4CECF; Tue, 5 Nov 2024 16:31:10 +0000 (UTC) Date: Tue, 5 Nov 2024 11:31:11 -0500 From: Steven Rostedt To: Marco Elver Cc: Kees Cook , Masami Hiramatsu , Mathieu Desnoyers , Andrew Morton , Oleg Nesterov , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Dmitry Vyukov , kasan-dev@googlegroups.com Subject: Re: [PATCH] tracing: Add task_prctl_unknown tracepoint Message-ID: <20241105113111.76c46806@gandalf.local.home> In-Reply-To: <20241105133610.1937089-1-elver@google.com> References: <20241105133610.1937089-1-elver@google.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 5 Nov 2024 14:34:05 +0100 Marco Elver wrote: > prctl() is a complex syscall which multiplexes its functionality based > on a large set of PR_* options. Currently we count 64 such options. The > return value of unknown options is -EINVAL, and doesn't distinguish from > known options that were passed invalid args that also return -EINVAL. > > To understand if programs are attempting to use prctl() options not yet > available on the running kernel, provide the task_prctl_unknown > tracepoint. > > Note, this tracepoint is in an unlikely cold path, and would therefore > be suitable for continuous monitoring (e.g. via perf_event_open). > > While the above is likely the simplest usecase, additionally this > tracepoint can help unlock some testing scenarios (where probing > sys_enter or sys_exit causes undesirable performance overheads): > > a. unprivileged triggering of a test module: test modules may register a > probe to be called back on task_prctl_unknown, and pick a very large > unknown prctl() option upon which they perform a test function for an > unprivileged user; > > b. unprivileged triggering of an eBPF program function: similar > as idea (a). > > Example trace_pipe output: > > <...>-366 [004] ..... 146.439400: task_prctl_unknown: pid=366 comm=a.out option=1234 arg2=101 arg3=102 arg4=103 arg5=104 ^^^ ^^^ > > Signed-off-by: Marco Elver > --- > include/trace/events/task.h | 43 +++++++++++++++++++++++++++++++++++++ > kernel/sys.c | 3 +++ > 2 files changed, 46 insertions(+) > > diff --git a/include/trace/events/task.h b/include/trace/events/task.h > index 47b527464d1a..ab711e581094 100644 > --- a/include/trace/events/task.h > +++ b/include/trace/events/task.h > @@ -56,6 +56,49 @@ TRACE_EVENT(task_rename, > __entry->newcomm, __entry->oom_score_adj) > ); > > +/** > + * task_prctl_unknown - called on unknown prctl() option > + * @task: pointer to the current task > + * @option: option passed > + * @arg2: arg2 passed > + * @arg3: arg3 passed > + * @arg4: arg4 passed > + * @arg5: arg5 passed > + * > + * Called on an unknown prctl() option. > + */ > +TRACE_EVENT(task_prctl_unknown, > + > + TP_PROTO(struct task_struct *task, int option, unsigned long arg2, unsigned long arg3, > + unsigned long arg4, unsigned long arg5), > + > + TP_ARGS(task, option, arg2, arg3, arg4, arg5), > + > + TP_STRUCT__entry( > + __field( pid_t, pid ) Why record the pid that is already recorded by the event header? > + __string( comm, task->comm ) I'm also surprised that the comm didn't show in the trace_pipe. I've updated the code so that it should usually find it. But saving it here may not be a big deal. -- Steve > + __field( int, option) > + __field( unsigned long, arg2) > + __field( unsigned long, arg3) > + __field( unsigned long, arg4) > + __field( unsigned long, arg5) > + ), > + > + TP_fast_assign( > + __entry->pid = task->pid; > + __assign_str(comm); > + __entry->option = option; > + __entry->arg2 = arg2; > + __entry->arg3 = arg3; > + __entry->arg4 = arg4; > + __entry->arg5 = arg5; > + ), > + > + TP_printk("pid=%d comm=%s option=%d arg2=%ld arg3=%ld arg4=%ld arg5=%ld", > + __entry->pid, __get_str(comm), __entry->option, > + __entry->arg2, __entry->arg3, __entry->arg4, __entry->arg5) > +); > + > #endif > > /* This part must be outside protection */ > diff --git a/kernel/sys.c b/kernel/sys.c > index 4da31f28fda8..dd0a71b68558 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -75,6 +75,8 @@ > #include > #include > > +#include > + > #include "uid16.h" > > #ifndef SET_UNALIGN_CTL > @@ -2785,6 +2787,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, > error = RISCV_SET_ICACHE_FLUSH_CTX(arg2, arg3); > break; > default: > + trace_task_prctl_unknown(me, option, arg2, arg3, arg4, arg5); > error = -EINVAL; > break; > }