From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 8F0C74908D5 for ; Sat, 25 Jul 2026 21:52:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785016359; cv=none; b=bLiZjOll3UxtVJJ8gmROt6prZkHguMQ9HIvG1cJxPnh8OefyhUTWMS4ExV3NA0EWwOhvt/rT8LqwFxng09Ytjfgto5aBeRXfTMh3a9Zj7TqpJAIicWvdct0rlengZ9EuwQCs/27gchA6uvf7a1DB6kSIFxI30lu0cw42xJhet8A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785016359; c=relaxed/simple; bh=h8mckCgan5zs1Vu4TqMmkLFiEF0RNhX3qgm32CM6ORo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=J0A1Bv7vlux+0jLI4ZeLhWMy5ye/B5tPpTtPVpURYlj6bnhpkM9fni5gr1onABbNX3ryOAJnUuYOH6y/ShE9EX35ujdkrzMW9qsdxHcdAgJuk/c+OgHRsrSsO3XHCgCWtRWPAhRAzibHWBTw60Eet1hbPmJ+CmZeEbSJCQpiQmM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JZrXlUef; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JZrXlUef" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 12A851F000E9; Sat, 25 Jul 2026 21:52:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785016358; bh=8GJwiQdxqB6w/7li4Yr/F7HazRQziSCanO3/QiOQEG4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JZrXlUefDmnh6irNgZZydQ8DyR8AUikQEi7ejBkq+CZ/HNFlgyN+cVz1dbG2W6vRX d0GY7fFrNAFr6lRRpJJvYgjJh8Fm4viu7ek3XF3+NcNj6gN1Ve1KeiO0hyi5TByK5J 6FdslTQXizrkMFtcA/QZ8ReBKOAiSezxA6CveJqXdA6GYvcgwQZz285wGtEqozMfI0 fOYXb7+C+ZKjbcj9dg36xyFGad6enKVs5JSTSPWpG2JBjrGUZPiKPePFjTugF0VULw HrQQV+gDSZfANqDlCiVAQgD5XLeVj8wbn90M/sycwPYzXmd9/gh1McsMowsOZuFHxT rUVbWr2leRoiA== From: SJ Park To: sashiko-bot@kernel.org Cc: SJ Park , damon@lists.linux.dev Subject: Re: [RFC PATCH 07/17] mm/damon/core: introduce damon_operations->prep_probes() Date: Sat, 25 Jul 2026 14:52:28 -0700 Message-ID: <20260725215230.131687-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260725211414.8ED581F000E9@smtp.kernel.org> References: Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Sat, 25 Jul 2026 21:14:14 +0000 sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: > - [Medium] prep_probes receives has_prep instead of access_check_disabled && has_prep, causing it to overwrite sampling_addr during normal access checking. > - [Medium] Uninitialized sampling_addr usage in apply_probes if prep_probes is not implemented. > -- > > --- Patch [7]: [RFC PATCH 07/17] mm/damon/core: introduce damon_operations->prep_probes() --- > commit 62e96fea7e813101fb4353abda03a93a90ef358a > Author: SJ Park > > mm/damon/core: introduce damon_operations->prep_probes() > > damon_prep needs to be executed by the underlying DAMON operation set. > Extend the operation set callback list for the execution of damon_prep > actions. If the underlying operation set implements the callback, DAMON > core executes it in the monitoring preparation time. > > > diff --git a/mm/damon/core.c b/mm/damon/core.c > > index 127d3a7c27280..d5b1e0b5851a1 100644 > > --- a/mm/damon/core.c > > +++ b/mm/damon/core.c > > [ ... ] > > > @@ -3878,6 +3891,8 @@ static int kdamond_fn(void *data) > > > > if (!access_check_disabled && ctx->ops.prepare_access_checks) > > ctx->ops.prepare_access_checks(ctx); > > + if (ctx->ops.prep_probes) > > + ctx->ops.prep_probes(ctx, has_prep); > > [Severity: Medium] > Could this overwrite the tracked sampling_addr during normal access checking? > > If a configuration has a prep without probe weights, access_check_disabled > is false and has_prep is true. prepare_access_checks() sets sampling_addr > and marks it for tracking. > > If prep_probes() is implemented by a backend, passing has_prep (true) here > instead of access_check_disabled && has_prep would cause it to generate > a new, unprepared sampling_addr that silently overwrites the tracked one. Good check. > > > > > kdamond_usleep(sample_interval); > > ctx->passed_sample_intervals++; > > @@ -3892,7 +3907,8 @@ static int kdamond_fn(void *data) > > else > > get_max_wsum = false; > > max_wsum = ctx->ops.apply_probes(ctx, > > - access_check_disabled, get_max_wsum); > > + access_check_disabled && !has_prep, > > + get_max_wsum); > > [Severity: Medium] > Does this result in uninitialized sampling_addr usage in apply_probes() if > the backend doesn't implement prep_probes? > > If a probe has a weight and a prep, both access_check_disabled and has_prep > evaluate to true, which skips prepare_access_checks(). > > If the current operations do not implement prep_probes > (ctx->ops.prep_probes == NULL), that callback is also skipped. > > When apply_probes() is called, set_samples evaluates to false (because > access_check_disabled && !has_prep is false). As a result, no function > initializes r->sampling_addr, and the uninitialized memory could be read > by apply_probes(). Again, good finding. I will fix above two like below. ''' --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -4251,7 +4251,7 @@ static int kdamond_fn(void *data) unsigned long next_ops_update_sis = ctx->next_ops_update_sis; unsigned long sample_interval = ctx->attrs.sample_interval; bool access_check_disabled = damon_has_probe_weights(ctx); - bool has_prep = damon_has_prep(ctx); + bool do_prep = damon_has_prep(ctx) && ctx->ops.prep_probes; unsigned int max_merge_score = 0, max_wsum; bool get_max_wsum; @@ -4260,8 +4260,8 @@ static int kdamond_fn(void *data) if (!access_check_disabled && ctx->ops.prepare_access_checks) ctx->ops.prepare_access_checks(ctx); - if (ctx->ops.prep_probes) - ctx->ops.prep_probes(ctx, has_prep); + if (do_prep) + ctx->ops.prep_probes(ctx, access_check_disabled); kdamond_usleep(sample_interval); ctx->passed_sample_intervals++; @@ -4283,7 +4283,7 @@ static int kdamond_fn(void *data) else get_max_wsum = false; max_wsum = ctx->ops.apply_probes(ctx, - access_check_disabled && !has_prep, + access_check_disabled && !do_prep, get_max_wsum); if (get_max_wsum) max_merge_score = max_wsum; ''' > > > if (get_max_wsum) > > max_merge_score = max_wsum; > > } > > -- > Sashiko AI review ยท https://sashiko.dev/#/patchset/20260725210225.129944-1-sj@kernel.org?part=7 Thanks, SJ