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 4480E386C36 for ; Sat, 16 May 2026 22:12:43 +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=1778969563; cv=none; b=B1EOUDtX27ChxgRjlOP0S7AoOdJqdvKh46Wy2PKDxBl8zo40O7avHm2dk0LPJhJabV7gKwxh9s4c+2zjsC4ThwSpMli6xEOWupFzaPZRXDSvvtcXw5X4n4OH5dj2V7pn2dTJLMvCwbb9pIUBb6S09jberWP7h+9Vg1WjjGduW2o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778969563; c=relaxed/simple; bh=yGrbL0nsyYDONWU2QcZPYVudZ1oeLwMEmKD+rgA4S3M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=bT7L8ZkTXlZcrLpBQjmILx6o5V3ZwjUhyHIqPCwDQwmBwlnxztevTwlCERMWTd3dca0W4FQvJlLuKDoIrPqD+FZ/yIEcUlUhAjkyY8hpZi9PNg9hiqUNZHNndSF/+2kOtosqqOjYH5DfYp1Ygd7UNjGMTEqW3sSYdToTUH4xVeQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=tQCYMYaE; 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="tQCYMYaE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C4C5BC19425; Sat, 16 May 2026 22:12:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778969562; bh=yGrbL0nsyYDONWU2QcZPYVudZ1oeLwMEmKD+rgA4S3M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tQCYMYaES5nQ2RqE86exk32AxJU/CpncMaDEsm5GIqO2QEBDPWIiieiq8/7UiXd3T nsjmJv0w8Uhv7qRRP8tIYIl5G8chCWDfdygykCXWFfsHBp5oXyM1K+dX0IIM/vbGQv lsiY2wti/m0HfG4BAygxVVm2KbyDpgpFQCTtzI3VLZviyf9OBRuI+HCQmhepGzNQjR GaQftkkVylt6zaMfgeglVT5vDUcJM3rWM8P9Q3X91VEX/dKRHQigef5lLqWxCobAZT PD0WbNOiu/r57FaDvEDvsHqfPxqQ8dJopRpCf78kvr+V/u7RtcIX+tlaldqslgyNLo RLcZZa9/hHKiw== From: SeongJae Park To: sashiko-bot@kernel.org Cc: SeongJae Park , damon@lists.linux.dev Subject: Re: [RFC PATCH] mm/damon/sysfs-schemes: delete tried region in regions_rmdirs() Date: Sat, 16 May 2026 15:12:34 -0700 Message-ID: <20260516221235.4589-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260516213959.28859C19425@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, 16 May 2026 21:39:58 +0000 sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [High] Moving `list_del()` out of the kobject release callback causes a Use-After-Free when `kobject_init_and_add()` fails in `damos_sysfs_populate_region_dir()`. > -- > > commit 97136b36d31f71cb6972114db84fe86abd95246f > Author: SeongJae Park > Subject: mm/damon/sysfs-schemes: delete tried region in regions_rmdirs() > > DAMON sysfs maintains the DAMOS tried region directory objects via a > linked list. When the user requests refresh of the directories, DAMON > sysfs removes all the region directories first, and then generate > updated regions directory on the empty space. Deletion of the container > region object from the linked list is now done inside the removal function > instead of the kobj release callback. > > [1] https://lore.kernel.org/20260513011920.119183-1-sj@kernel.org > > > diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c > > index 622c3799db87b..aefeb5d22fb7d 100644 > > --- a/mm/damon/sysfs-schemes.c > > +++ b/mm/damon/sysfs-schemes.c > > @@ -88,7 +88,6 @@ static void damon_sysfs_scheme_region_release(struct kobject *kobj) > > struct damon_sysfs_scheme_region *region = container_of(kobj, > > struct damon_sysfs_scheme_region, kobj); > > > > - list_del(®ion->list); > > kfree(region); > > } > > Does removing list_del() here cause a use-after-free if kobject_init_and_add() > fails in damos_sysfs_populate_region_dir()? > > If kobject_init_and_add() fails, the error path drops the reference: > > mm/damon/sysfs-schemes.c:damos_sysfs_populate_region_dir() { > ... > list_add_tail(®ion->list, &sysfs_regions->regions_list); > sysfs_regions->nr_regions++; > if (kobject_init_and_add(®ion->kobj, > &damon_sysfs_scheme_region_ktype, > &sysfs_regions->kobj, "%d", > sysfs_regions->nr_regions++)) { > kobject_put(®ion->kobj); > } > ... > } > > Because region is added to the list before kobject_init_and_add(), dropping > the reference will free the region, but it remains in regions_list since > the release callback no longer unlinks it. Good finding. I wrote this patch on a tree having the data attributes monitoring, which moved the list_add_tail() call to be done after kobject_init_and_add() success, so missed this. > > Should we add an explicit list_del(®ion->list) in the error path of > damos_sysfs_populate_region_dir() to prevent list corruption? I will move list_add_tail() call to be done after kobject_init_and_add() success. > > -- > Sashiko AI review ยท https://sashiko.dev/#/patchset/20260516211436.1883-1-sj@kernel.org?part=1 Thanks, SJ