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 D9138137E; Fri, 19 Apr 2024 02:33:09 +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=1713493990; cv=none; b=HXG2IloqH5+25w5BOfzWsQomT6t3H34JmvPNJEbt0Sklqy8IcsOXyu1Qbxqbd0d0IyfDi/IRAxNVHzZV+79irS2ERC+SN6ccqZGXxadBdzU/dMcH7lmcTNcnKByTeIF+8GxRp/IFO+0ijUKolQMAcjIk2WL9WHv40tEft+E+twc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713493990; c=relaxed/simple; bh=b32gB5mmLTgH83geBuB0IJ9qfWDbzBC9We7CLDKlGIM=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=itdlSTXOs2Er29+/3+OHmRW53LEMP2qOmWOGh8j2AG1YugCw7/nsFMRrGEETsCf6w0oMq8ba9Tj2O5LbT6h/HsjVmmqt0/dIHYNtIchHH4n+c5Cn6zSazKzlZzzBHGY14StKNTkwG/82t/R9e16BcZiKu5LMA3JzsQoBEU3yZro= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JHVjW4vq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JHVjW4vq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 85116C113CC; Fri, 19 Apr 2024 02:33:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713493989; bh=b32gB5mmLTgH83geBuB0IJ9qfWDbzBC9We7CLDKlGIM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=JHVjW4vqRTa3mRYpGwC6FQY2ORkbGjTCr7HbIXGGBUW1ojkPxX6skMIscw7qEseuy XGlOc+8YwbJ4pmfanEkIkj0oIYJBI+8FC2DkViIBmT9eU//SmlEpLvgvpnTSHBouBK pETj3z8khr4MzG+l35+wDVqEUbr7XOeesa/1L5A+jFQX2GsDnPoQyfGaKxEirF9AzO DPsIpT3l2aKV26vw1iQQjftLL2Gq5qAxcmY3PUKzoVAabkMWtFc6bTqaDwpQgcl888 pMSktzgnrwCTb58Nb2g7XFZCSa+aEyDZJXkbyVUpESTkPPKKVqBPmNVZ12XFGKPvBO YiZEH2D5zwq5g== Date: Fri, 19 Apr 2024 11:33:05 +0900 From: Masami Hiramatsu (Google) To: Beau Belgrave Cc: rostedt@goodmis.org, mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, dcook@linux.microsoft.com Subject: Re: [PATCH 1/2] tracing/user_events: Fix non-spaced field matching Message-Id: <20240419113305.7b0ae2b11395eec16b5c15b6@kernel.org> In-Reply-To: <20240416224102.734-2-beaub@linux.microsoft.com> References: <20240416224102.734-1-beaub@linux.microsoft.com> <20240416224102.734-2-beaub@linux.microsoft.com> X-Mailer: Sylpheed 3.7.0 (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, 16 Apr 2024 22:41:01 +0000 Beau Belgrave wrote: > When the ABI was updated to prevent same name w/different args, it > missed an important corner case when fields don't end with a space. > Typically, space is used for fields to help separate them, like > "u8 field1; u8 field2". If no spaces are used, like > "u8 field1;u8 field2", then the parsing works for the first time. > However, the match check fails on a subsequent register, leading to > confusion. > > This is because the match check uses argv_split() and assumes that all > fields will be split upon the space. When spaces are used, we get back > { "u8", "field1;" }, without spaces we get back { "u8", "field1;u8" }. > This causes a mismatch, and the user program gets back -EADDRINUSE. > > Add a method to detect this case before calling argv_split(). If found > force a space after the field separator character ';'. This ensures all > cases work properly for matching. > > With this fix, the following are all treated as matching: > u8 field1;u8 field2 > u8 field1; u8 field2 > u8 field1;\tu8 field2 > u8 field1;\nu8 field2 Sounds good to me. I just have some nits. > > Fixes: ba470eebc2f6 ("tracing/user_events: Prevent same name but different args event") > Signed-off-by: Beau Belgrave > --- > kernel/trace/trace_events_user.c | 88 +++++++++++++++++++++++++++++++- > 1 file changed, 87 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c > index 70d428c394b6..9184d3962b2a 100644 > --- a/kernel/trace/trace_events_user.c > +++ b/kernel/trace/trace_events_user.c > @@ -1989,6 +1989,92 @@ static int user_event_set_tp_name(struct user_event *user) > return 0; > } > > +/* > + * Counts how many ';' without a trailing space are in the args. > + */ > +static int count_semis_no_space(char *args) > +{ > + int count = 0; > + > + while ((args = strchr(args, ';'))) { > + args++; > + > + if (!isspace(*args)) > + count++; > + } > + > + return count; > +} > + > +/* > + * Copies the arguments while ensuring all ';' have a trailing space. > + */ > +static char *fix_semis_no_space(char *args, int count) nit: This name does not represent what it does. 'insert_space_after_semis()' is more self-described. > +{ > + char *fixed, *pos; > + char c, last; > + int len; > + > + len = strlen(args) + count; > + fixed = kmalloc(len + 1, GFP_KERNEL); > + > + if (!fixed) > + return NULL; > + > + pos = fixed; > + last = '\0'; > + > + while (len > 0) { > + c = *args++; > + > + if (last == ';' && !isspace(c)) { > + *pos++ = ' '; > + len--; > + } > + > + if (len > 0) { > + *pos++ = c; > + len--; > + } > + > + last = c; > + } nit: This loop can be simpler, because we are sure fixed has enough length; /* insert a space after ';' if there is no space. */ while(*args) { *pos = *args++; if (*pos++ == ';' && !isspace(*args)) *pos++ = ' '; } > + > + /* > + * len is the length of the copy excluding the null. > + * This ensures we always have room for a null. > + */ > + *pos = '\0'; > + > + return fixed; > +} > + > +static char **user_event_argv_split(char *args, int *argc) > +{ > + /* Count how many ';' without a trailing space */ > + int count = count_semis_no_space(args); > + > + if (count) { nit: it is better to exit fast, so if (!count) return argv_split(GFP_KERNEL, args, argc); ... Thank you, OT: BTW, can this also simplify synthetic events? > + /* We must fixup 'field;field' to 'field; field' */ > + char *fixed = fix_semis_no_space(args, count); > + char **split; > + > + if (!fixed) > + return NULL; > + > + /* We do a normal split afterwards */ > + split = argv_split(GFP_KERNEL, fixed, argc); > + > + /* We can free since argv_split makes a copy */ > + kfree(fixed); > + > + return split; > + } > + > + /* No fixup is required */ > + return argv_split(GFP_KERNEL, args, argc); > +} > + > /* > * Parses the event name, arguments and flags then registers if successful. > * The name buffer lifetime is owned by this method for success cases only. > @@ -2012,7 +2098,7 @@ static int user_event_parse(struct user_event_group *group, char *name, > return -EPERM; > > if (args) { > - argv = argv_split(GFP_KERNEL, args, &argc); > + argv = user_event_argv_split(args, &argc); > > if (!argv) > return -ENOMEM; > -- > 2.34.1 > -- Masami Hiramatsu (Google)