linux-kernel - Re: [PATCH V3] tracing/user_events: Prevent same name but different args event

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Message-ID: <20230530181011.GA225@W11-BEAU-MD.localdomain>
Date:   Tue, 30 May 2023 11:10:11 -0700
From:   Beau Belgrave <beaub@...ux.microsoft.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     sunliming <sunliming@...inos.cn>, rostedt@...dmis.org,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH V3] tracing/user_events: Prevent same name but different
 args event

On Mon, May 29, 2023 at 06:23:19PM +0900, Masami Hiramatsu wrote:
> On Mon, 29 May 2023 11:21:00 +0800
> sunliming <sunliming@...inos.cn> wrote:
> 
> > User processes register name_args for events. If the same name but different
> > args event are registered. The trace outputs of second event are printed
> > as the first event. This is incorrect.
> > 
> > Return EADDRINUSE back to the user process if the same name but different args
> > event has being registered.
> > 
> > Signed-off-by: sunliming <sunliming@...inos.cn>
> 
> Looks good to me.
> 
> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Thank you,
> 

This also looks good to me, thank you for your patch!

Acked-by: Beau Belgrave <beaub@...ux.microsoft.com>

Thanks,
-Beau

> > ---
> >  kernel/trace/trace_events_user.c              | 36 +++++++++++++++----
> >  .../selftests/user_events/ftrace_test.c       |  6 ++++
> >  2 files changed, 36 insertions(+), 6 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> > index b1ecd7677642..e90161294698 100644
> > --- a/kernel/trace/trace_events_user.c
> > +++ b/kernel/trace/trace_events_user.c
> > @@ -1753,6 +1753,8 @@ static int user_event_parse(struct user_event_group *group, char *name,
> >  	int ret;
> >  	u32 key;
> >  	struct user_event *user;
> > +	int argc = 0;
> > +	char **argv;
> >  
> >  	/* Prevent dyn_event from racing */
> >  	mutex_lock(&event_mutex);
> > @@ -1760,13 +1762,35 @@ static int user_event_parse(struct user_event_group *group, char *name,
> >  	mutex_unlock(&event_mutex);
> >  
> >  	if (user) {
> > -		*newuser = user;
> > -		/*
> > -		 * Name is allocated by caller, free it since it already exists.
> > -		 * Caller only worries about failure cases for freeing.
> > -		 */
> > -		kfree(name);
> > +		if (args) {
> > +			argv = argv_split(GFP_KERNEL, args, &argc);
> > +			if (!argv) {
> > +				ret = -ENOMEM;
> > +				goto error;
> > +			}
> > +
> > +			ret = user_fields_match(user, argc, (const char **)argv);
> > +			argv_free(argv);
> > +
> > +		} else
> > +			ret = list_empty(&user->fields);
> > +
> > +		if (ret) {
> > +			*newuser = user;
> > +			/*
> > +			 * Name is allocated by caller, free it since it already exists.
> > +			 * Caller only worries about failure cases for freeing.
> > +			 */
> > +			kfree(name);
> > +		} else {
> > +			ret = -EADDRINUSE;
> > +			goto error;
> > +		}
> > +
> >  		return 0;
> > +error:
> > +		refcount_dec(&user->refcnt);
> > +		return ret;
> >  	}
> >  
> >  	user = kzalloc(sizeof(*user), GFP_KERNEL_ACCOUNT);
> > diff --git a/tools/testing/selftests/user_events/ftrace_test.c b/tools/testing/selftests/user_events/ftrace_test.c
> > index 7c99cef94a65..6e8c4b47281c 100644
> > --- a/tools/testing/selftests/user_events/ftrace_test.c
> > +++ b/tools/testing/selftests/user_events/ftrace_test.c
> > @@ -228,6 +228,12 @@ TEST_F(user, register_events) {
> >  	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
> >  	ASSERT_EQ(0, reg.write_index);
> >  
> > +	/* Multiple registers to same name but different args should fail */
> > +	reg.enable_bit = 29;
> > +	reg.name_args = (__u64)"__test_event u32 field1;";
> > +	ASSERT_EQ(-1, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
> > +	ASSERT_EQ(EADDRINUSE, errno);
> > +
> >  	/* Ensure disabled */
> >  	self->enable_fd = open(enable_file, O_RDWR);
> >  	ASSERT_NE(-1, self->enable_fd);
> > -- 
> > 2.25.1
> > 
> 
> 
> -- 
> Masami Hiramatsu (Google) <mhiramat@...nel.org>