From: Steven Rostedt <rostedt@goodmis.org>
To: Kees Cook <keescook@chromium.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Next Mailing List <linux-next@vger.kernel.org>
Subject: Re: linux-next: build failure after merge of the kspp tree
Date: Tue, 25 Jan 2022 16:23:26 -0500 [thread overview]
Message-ID: <20220125162326.3d1ca960@gandalf.local.home> (raw)
In-Reply-To: <202201251256.CCCBE9851E@keescook>
On Tue, 25 Jan 2022 12:57:24 -0800
Kees Cook <keescook@chromium.org> wrote:
> On Tue, Jan 25, 2022 at 11:31:54PM +0900, Masami Hiramatsu wrote:
> > On Tue, 25 Jan 2022 22:27:32 +0900
> > Masami Hiramatsu <mhiramat@kernel.org> wrote:
> >
> > > > /*
> > > > * struct trace_event_data_offsets_<call> {
> > > > * u32 <item1>;
> > > > * u32 <item2>;
> > > > * [...]
> > > > * };
> > > > *
> > > > * The __dynamic_array() macro will create each u32 <item>, this is
> > > > * to keep the offset of each array from the beginning of the event.
> > > > * The size of an array is also encoded, in the higher 16 bits of
> > > > * <item>.
> > > > */
> > > >
> > > > So, I think -Warray-bounds is refusing to see the destination as
> > > > anything except a u32, but being accessed at 4 (sizeof(u32)) + 8
> > > > (address && 0xffff) (?)
> > >
> > > Ah, I got it. Yes, that's right. __data_loc() will access the data
> > > from the __entry, but the __rel_loc() points the same address from
> > > the encoded field ("__rel_loc_foo" in this case) itself.
> > > This is introduced for the user application event, which doesn't
> > > know the actual __entry size because the __entry includes some
> > > kernel internal defined fields.
> > >
> > > > But if this is true, I would imagine there would be plenty of other
> > > > warnings? I'm currently stumped.
> > >
> > > That is because __rel_loc is used only in the sample code in the kernel
> > > for testing. Other use-cases comes from user-space.
> > > Hmm, can we skip this boundary check for this example?
> >
> > If the -Warray-bounds determines the destination array size from
> > the type of given pointer, we can just change the macro as below;
> >
> > #define __get_rel_dynamic_array(field)
> > ((void *)__entry + \
> > offsetof(typeof(*__entry), __rel_loc_##field) + \
> > sizeof(__entry->__rel_loc_##field) + \
> > (__entry->__rel_loc_##field & 0xffff))
> >
> > This must works same as __get_dynamic_array() macro.
> >
> > Could you try this patch?
> >
> > From 2982ba01367ec1f746a4f128512436e5325a7f9d Mon Sep 17 00:00:00 2001
> > From: Masami Hiramatsu <mhiramat@kernel.org>
> > Date: Tue, 25 Jan 2022 23:19:30 +0900
> > Subject: [PATCH] tracing: Avoid -Warray-bounds warning for __rel_loc macro
> >
> > Since -Warray-bounds checks the destination size from the
> > type of given pointer, __assign_rel_str() macro gets warned
> > because it passes the pointer to the 'u32' field instead of
> > 'trace_event_raw_*' data structure.
> > Pass the data address calculated from the 'trace_event_raw_*'
> > instead of 'u32' __rel_loc field.
> >
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> > Cc: Kees Cook <keescook@chromium.org>
> > ---
> > include/trace/trace_events.h | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h
> > index 8c6f7c433518..65d927e059d3 100644
> > --- a/include/trace/trace_events.h
> > +++ b/include/trace/trace_events.h
> > @@ -318,9 +318,10 @@ TRACE_MAKE_SYSTEM_STR();
> > #define __get_str(field) ((char *)__get_dynamic_array(field))
> >
> > #undef __get_rel_dynamic_array
> > -#define __get_rel_dynamic_array(field) \
> > - ((void *)(&__entry->__rel_loc_##field) + \
> > - sizeof(__entry->__rel_loc_##field) + \
> > +#define __get_rel_dynamic_array(field) \
> > + ((void *)__entry + \
> > + offsetof(typeof(*__entry), __rel_loc_##field) + \
> > + sizeof(__entry->__rel_loc_##field) + \
> > (__entry->__rel_loc_##field & 0xffff))
> >
> > #undef __get_rel_dynamic_array_len
>
> This patch doesn't silence the warning, but now that I see the shape of
> things more clearly, let me see if I can find the right combo.
Hmm, could the zero size array cause an issues here. That is, does this
help?
diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h
index 65d927e059d3..3d29919045af 100644
--- a/include/trace/trace_events.h
+++ b/include/trace/trace_events.h
@@ -128,7 +128,7 @@ TRACE_MAKE_SYSTEM_STR();
struct trace_event_raw_##name { \
struct trace_entry ent; \
tstruct \
- char __data[0]; \
+ char __data[]; \
}; \
\
static struct trace_event_class event_class_##name;
-- Steve
next prev parent reply other threads:[~2022-01-25 21:23 UTC|newest]
Thread overview: 108+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-25 3:50 linux-next: build failure after merge of the kspp tree Stephen Rothwell
2022-01-25 7:44 ` Kees Cook
2022-01-25 13:27 ` Masami Hiramatsu
2022-01-25 14:01 ` Steven Rostedt
2022-01-25 17:53 ` Kees Cook
2022-01-25 14:31 ` Masami Hiramatsu
2022-01-25 15:49 ` Steven Rostedt
2022-01-25 17:54 ` Kees Cook
2022-01-25 18:41 ` Steven Rostedt
2022-01-25 20:57 ` Kees Cook
2022-01-25 21:23 ` Steven Rostedt [this message]
2022-01-25 21:28 ` Steven Rostedt
2022-01-25 22:07 ` Kees Cook
2022-01-25 22:21 ` Steven Rostedt
2022-01-26 0:35 ` Masami Hiramatsu
2022-01-26 1:16 ` Steven Rostedt
2022-01-26 3:18 ` Kees Cook
2022-01-26 3:26 ` Steven Rostedt
2022-01-26 19:41 ` Beau Belgrave
2022-01-26 21:00 ` Steven Rostedt
2022-01-26 3:52 ` Masami Hiramatsu
2022-01-26 4:06 ` Steven Rostedt
2022-01-26 3:17 ` Kees Cook
2022-01-25 22:01 ` Kees Cook
-- strict thread matches above, loose matches on Subject: below --
2024-03-05 3:50 Stephen Rothwell
2024-03-05 9:54 ` Kees Cook
2023-09-14 1:50 Stephen Rothwell
2023-09-14 3:07 ` Kees Cook
2023-01-05 2:25 Stephen Rothwell
2023-01-05 3:22 ` Kees Cook
2023-01-05 4:24 ` Stephen Rothwell
2022-12-01 3:07 Stephen Rothwell
2022-12-01 16:31 ` Kees Cook
2022-07-28 10:55 Stephen Rothwell
2022-07-28 15:12 ` Matthias Kaehlcke
2022-05-05 7:40 Stephen Rothwell
2022-05-07 17:18 ` Kees Cook
2022-03-16 7:32 Stephen Rothwell
2022-03-17 1:01 ` Linus Walleij
2022-03-17 8:24 ` Marc Zyngier
2022-03-09 10:10 Stephen Rothwell
2022-03-09 16:52 ` Kees Cook
2022-03-09 16:58 ` Hans de Goede
2022-03-09 17:18 ` Kees Cook
2022-02-28 22:27 Stephen Rothwell
2022-02-28 23:02 ` Kees Cook
2022-03-02 9:16 ` Stephen Rothwell
2022-03-03 7:29 ` Stephen Rothwell
2022-01-30 23:09 Stephen Rothwell
2022-01-31 4:04 ` Kees Cook
2022-01-31 4:59 ` Stephen Rothwell
2022-01-31 6:19 ` Kees Cook
2022-01-31 19:10 ` Saeed Mahameed
2022-01-31 21:06 ` Kees Cook
2022-01-30 22:34 Stephen Rothwell
2022-01-30 23:24 ` Herbert Xu
2022-01-31 0:15 ` Stephen Rothwell
2022-01-31 0:20 ` Herbert Xu
2022-01-31 0:41 ` Stephen Rothwell
2022-01-25 3:24 Stephen Rothwell
2022-01-25 3:43 ` Kees Cook
2022-02-08 4:42 ` Stephen Rothwell
2022-02-08 6:13 ` Kees Cook
2022-01-25 2:55 Stephen Rothwell
2022-01-25 3:02 ` Stephen Rothwell
2022-01-25 3:22 ` Kees Cook
2022-01-25 0:57 Stephen Rothwell
2022-01-25 3:35 ` Kees Cook
2022-01-25 14:07 ` David Sterba
2021-09-16 3:34 Stephen Rothwell
2021-09-16 6:00 ` Kees Cook
2021-08-26 7:52 Stephen Rothwell
2021-08-26 15:38 ` Kees Cook
2020-06-23 3:51 Stephen Rothwell
2020-06-23 3:56 ` David Miller
2020-06-21 13:48 Stephen Rothwell
2020-06-21 15:36 ` Kees Cook
2018-07-27 9:02 Stephen Rothwell
2018-07-27 9:06 ` Stephen Rothwell
2018-07-27 10:55 ` Stephen Rothwell
2018-07-27 12:55 ` Will Deacon
2018-07-27 13:01 ` Will Deacon
2018-07-27 13:27 ` Will Deacon
2018-07-27 16:00 ` Kees Cook
2018-07-30 7:33 ` Stephen Rothwell
2018-07-30 14:47 ` Laura Abbott
2018-07-30 16:37 ` Will Deacon
2018-07-31 10:09 ` Will Deacon
2018-07-31 11:27 ` Stephen Rothwell
2017-11-08 5:23 Stephen Rothwell
2017-11-08 23:43 ` Kees Cook
2017-11-09 0:18 ` Darrick J. Wong
2017-11-09 0:31 ` Kees Cook
2017-06-20 4:56 Stephen Rothwell
2017-06-20 5:39 ` Kees Cook
2017-06-20 5:42 ` John Johansen
2017-06-20 5:39 ` John Johansen
2017-06-26 18:19 ` Kees Cook
2017-06-27 3:33 ` James Morris
2017-06-27 22:16 ` Kees Cook
2017-06-28 5:48 ` James Morris
2017-06-16 1:30 Stephen Rothwell
2017-06-16 2:51 ` Daniel Micay
2017-06-16 2:52 ` Daniel Micay
2017-06-16 3:20 ` Kees Cook
2017-06-16 3:31 ` Stephen Rothwell
2017-06-19 0:23 ` Stephen Rothwell
2017-06-19 21:01 ` Kees Cook
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220125162326.3d1ca960@gandalf.local.home \
--to=rostedt@goodmis.org \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-next@vger.kernel.org \
--cc=mhiramat@kernel.org \
--cc=sfr@canb.auug.org.au \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).