From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnd Bergmann <arnd@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Arnd Bergmann <arnd@arndb.de>,
Adrian Hunter <adrian.hunter@intel.com>,
Tobias Klauser <tklauser@distanz.ch>,
Wei Yang <richard.weiyang@linux.alibaba.com>,
Chengming Zhou <zhouchengming@bytedance.com>,
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
linux-kernel@vger.kernel.org, Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH] ftrace: shut up -Wcast-function-type warning for ftrace_ops_no_ops
Date: Tue, 23 Mar 2021 16:25:07 +0100 [thread overview]
Message-ID: <YFoIU0xC3lXBwc9Y@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210323085742.18477aad@gandalf.local.home>
On Tue, Mar 23, 2021 at 08:57:42AM -0400, Steven Rostedt wrote:
> Well, from what I understand is that typecasting functions to other types
> of functions is one of the mistakes that cause security bugs to happen. And
> there's been a few of them in the kernel. Which is why the compilers have
> now been flagging them.
Doing the cast in the first pace is an indication something weird is
happening anyway. C will already warn you if you assign non-matching
pointer types.
So if there's bugs, audit all (function) pointer casts. Don't wreck
casts.
This warning will only make people add more (void *) intermediate casts
and then we have uglier code and an equal amount of hidden bugs. IE. we
really didn't win anything at all.
> This particular instance of the typecasting is unique and there's a bit of
> magic involved. Adding this little work around here is fine. Probably needs
> a better comment though.
Nah, it's not unique, static_call() has a whole bunch of them, including
the exact same you have. Yes, we're doing something C thinks is UB, but
we do that all day every day.
next prev parent reply other threads:[~2021-03-23 15:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 21:49 [PATCH] ftrace: shut up -Wcast-function-type warning for ftrace_ops_no_ops Arnd Bergmann
2021-03-22 22:00 ` Steven Rostedt
2021-03-23 7:39 ` Peter Zijlstra
2021-03-23 12:57 ` Steven Rostedt
2021-03-23 15:25 ` Peter Zijlstra [this message]
2021-03-23 16:05 ` Peter Zijlstra
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