linux-kernel - Re: [PATCH] perf: fix segfault in `lock contention -b`

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <fb38d19e-f4b4-4f89-a41a-78a845861468@amd.com>
Date: Tue, 13 Jan 2026 08:41:24 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Tycho Andersen <tycho@...nel.org>, Arnaldo Carvalho de Melo
	<acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>
CC: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Mark Rutland <mark.rutland@....com>, Alexander Shishkin
	<alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, "Ian
 Rogers" <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, "James
 Clark" <james.clark@...aro.org>, Chun-Tse Shao <ctshao@...gle.com>,
	<linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "Ravi
 Bangoria" <ravi.bangoria@....com>
Subject: Re: [PATCH] perf: fix segfault in `lock contention -b`

Hello Tycho,

On 1/9/2026 10:14 PM, Tycho Andersen wrote:
> @@ -43,19 +43,20 @@ static void check_slab_cache_iter(struct lock_contention *con)
>  	con->btf = btf__load_vmlinux_btf();
>  	if (con->btf == NULL) {
>  		pr_debug("BTF loading failed: %s\n", strerror(errno));
> -		return;
> +		return -errno;
>  	}
>  
>  	ret = btf__find_by_name_kind(con->btf, "bpf_iter__kmem_cache", BTF_KIND_STRUCT);
>  	if (ret < 0) {
>  		bpf_program__set_autoload(skel->progs.slab_cache_iter, false);
>  		pr_debug("slab cache iterator is not available: %d\n", ret);
> -		return;
> +		return ret;
>  	}
>  
>  	has_slab_iter = true;
>  
>  	bpf_map__set_max_entries(skel->maps.slab_caches, con->map_nr_entries);
> +	return 0;
>  }
>  
>  static void run_slab_cache_iter(void)
> @@ -301,7 +302,8 @@ int lock_contention_prepare(struct lock_contention *con)
>  			skel->rodata->use_cgroup_v2 = 1;
>  	}
>  
> -	check_slab_cache_iter(con);
> +	if (check_slab_cache_iter(con) < 0)
> +		return -1;
>  
>  	if (con->filters->nr_slabs && has_slab_iter) {

nit.

Now that lock_contention_prepare() bails out when
check_slab_cache_iter() fails, we no longer need the "has_slab_iter"
global indicator.

Both this, and run_slab_cache_iter() that depend on "has_slab_iter"
will only run if check_slab_cache_iter() succeeded and the global
indicator will be true in both those cases.

Can be separate follow-up cleanup.

>  		skel->rodata->has_slab = 1;
> 
> base-commit: 5572ad8fddecd4a0db19801262072ff5916b7589

-- 
Thanks and Regards,
Prateek