From: Petr Mladek <pmladek@suse.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Miguel Ojeda <ojeda@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
rust-for-linux <rust-for-linux@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Gary Guo <gary@garyguo.net>, Alex Gaynor <alex.gaynor@gmail.com>,
Wedson Almeida Filho <wedsonaf@google.com>,
Steven Rostedt <rostedt@goodmis.org>,
Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: Re: [PATCH v4 12/20] vsprintf: add new `%pA` format specifier
Date: Thu, 24 Feb 2022 10:55:33 +0100 [thread overview]
Message-ID: <YhdWFRGHpeOn+e0F@alley> (raw)
In-Reply-To: <10bbffc2-f144-8555-d41b-fede69a13c16@rasmusvillemoes.dk>
On Tue 2022-02-22 11:35:39, Rasmus Villemoes wrote:
> On 22/02/2022 10.29, Petr Mladek wrote:
> > On Mon 2022-02-14 13:12:24, Miguel Ojeda wrote:
> >> On Mon, Feb 14, 2022 at 11:52 AM Rasmus Villemoes
> >> <linux@rasmusvillemoes.dk> wrote:
> >>>
> >>> I think the point is for vsnprintf() to call (back) into Rust code.
> >>
> >> Indeed, this is the case.
> >>
> >>> That said, I don't like the !CONFIG_RUST version to return NULL, that
> >>> will surely crash moments later.
> >>>
> >>> So I prefer something like
> >>>
> >>> [rust.h]
> >>> // no CONFIG_RUST conditional
> >>> +char *rust_fmt_argument(char* buf, char* end, void *ptr);
> >>>
> >>> [vsprintf.c]
> >>> + case 'A':
> >>> + if (IS_ENABLED(CONFIG_RUST))
> >>> + return rust_fmt_argument(buf, end, ptr);
> >>> + else
> >>> + return string_nocheck(buf, end, "[%pA in non-Rust
> >>> code?!]", default_str_spec);
> >
> > Any long message might cause buffer overflow when the caller expects
> > fixed short string.
>
> If the caller (1) uses a %p extension from C code which should only be
> used from Rust and (2) uses sprintf() or another variant where he
> doesn't provide the real buffer bounds, well, then he certainly gets to
> keep the pieces.
>
> It is a much worse problem that if CONFIG_RUST is enabled, we can't know
> that we were actually called from Rust (but when !CONFIG_RUST, we
> certainly know that we weren't), so we could call into rust_fmt_argument
> with a pointer which certainly doesn't point to the/a data structure
> which that Rust code expects. But we can't do anything about it, we will
> just have to rely on static analysis to flag any use of %pA in C code.
Yeah. !CONFIG_RUST would trigger the warning and help to find the
sinners but it is not reliable. Static analysic might be better...
> > The most safe solution would be to use WARN_ONCE().
>
> Preferably no, we shouldn't call into the printk machinery from within
> vsnprintf(). I know I've added a few myself (AFAIR for use of %n or
> other unsupported specifiers, and for overflow of precision/field
> width), and I've often thought about a way to get rid of them while
> still making sure some message eventually gets logged (once).
WARN_ONCE() in vsprintf() code is much more acceptable these days
with the lockless ringbuffer.
Best Regards,
Petr
next prev parent reply other threads:[~2022-02-24 9:55 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-12 13:03 [PATCH v4 00/20] Rust support Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 01/20] kallsyms: support "big" kernel symbols Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 02/20] kallsyms: increase maximum kernel symbol length to 512 Miguel Ojeda
2022-02-22 8:19 ` Petr Mladek
2022-02-22 12:45 ` Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 03/20] kallsyms: use the correct buffer size for symbols Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 04/20] rust: add C helpers Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 05/20] rust: add `compiler_builtins` crate Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 06/20] rust: add `alloc` crate Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 07/20] rust: add `build_error` crate Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 08/20] rust: add `macros` crate Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 09/20] rust: add `kernel` crate's `sync` module Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 10/20] rust: add `kernel` crate Miguel Ojeda
2022-02-14 5:27 ` Sergey Senozhatsky
2022-02-14 13:36 ` Miguel Ojeda
2022-02-22 9:06 ` Petr Mladek
2022-02-22 12:48 ` Miguel Ojeda
2022-02-24 12:39 ` Petr Mladek
2022-02-12 13:03 ` [PATCH v4 11/20] rust: export generated symbols Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 12/20] vsprintf: add new `%pA` format specifier Miguel Ojeda
2022-02-14 10:18 ` Andy Shevchenko
2022-02-14 10:52 ` Rasmus Villemoes
2022-02-14 11:36 ` David Laight
2022-02-14 14:04 ` Miguel Ojeda
2022-02-14 12:12 ` Miguel Ojeda
2022-02-22 9:29 ` Petr Mladek
2022-02-22 10:35 ` Rasmus Villemoes
2022-02-24 9:55 ` Petr Mladek [this message]
2022-02-14 12:27 ` Miguel Ojeda
2022-02-14 13:54 ` Andy Shevchenko
2022-02-14 14:56 ` Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 13/20] scripts: add `generate_rust_analyzer.py` Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 14/20] scripts: decode_stacktrace: demangle Rust symbols Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 15/20] docs: add Rust documentation Miguel Ojeda
2022-02-14 10:47 ` Akira Yokosawa
2022-02-14 12:44 ` Miguel Ojeda
2022-02-16 13:37 ` Akira Yokosawa
2022-02-16 14:02 ` Miguel Ojeda
2022-03-17 8:19 ` Miguel Ojeda
2022-03-17 14:50 ` Akira Yokosawa
2022-03-18 13:12 ` Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 16/20] Kbuild: add Rust support Miguel Ojeda
2022-02-12 14:16 ` Russell King (Oracle)
2022-02-12 15:47 ` Miguel Ojeda
2022-02-12 16:18 ` Russell King (Oracle)
2022-02-12 18:32 ` Miguel Ojeda
2022-02-12 18:27 ` John Paul Adrian Glaubitz
2022-02-12 18:57 ` Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 17/20] samples: add Rust examples Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 18/20] MAINTAINERS: Rust Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 19/20] [RFC] drivers: gpio: PrimeCell PL061 in Rust Miguel Ojeda
2022-02-12 13:03 ` [PATCH v4 20/20] [RFC] drivers: android: Binder IPC " Miguel Ojeda
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