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Mon, 28 Jul 2025 11:04:58 -0700 (PDT) Message-ID: Date: Mon, 28 Jul 2025 11:04:56 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/5 cgroup/for-6.16-fixes] harden css_create() for safe placement of call to css_rstat_init() To: =?UTF-8?Q?Michal_Koutn=C3=BD?= Cc: tj@kernel.org, shakeel.butt@linux.dev, yosryahmed@google.com, hannes@cmpxchg.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, kernel-team@meta.com References: <20250722014030.297537-1-inwardvessel@gmail.com> Content-Language: en-US From: JP Kobryn In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Thanks for taking a look Michal. On 7/25/25 10:23 AM, Michal Koutný wrote: > Hi. > > On Mon, Jul 21, 2025 at 06:40:25PM -0700, JP Kobryn wrote: > ... > > Thanks for the instructive summary! > >> If any of the three goto jumps are taken, async cleanup will begin and >> css_rstat_exit() will be invoked. But since css_rstat_init() would not have >> succeeded, the warning will eventually be reached. > First thought is why not simply add a flag that'd guide whether > css_rstat_exit() has work to do. I did consider adding an "initialized" flag to the css but since there can be multiple css's per cgroup it felt like it would be adding overhead. So I went the path of getting the call sequence right. I'm open to feedback on this, though. > > This is meant as a fix, so it should have some metadata, I'd consider this one: > Fixes: 5da3bfa029d68 ("cgroup: use separate rstat trees for each subsystem") > > (that's when css_rstat_init was moved to css_create) > > and likely this > Reported-by: syzbot+8d052e8b99e40bc625ed@syzkaller.appspotmail.com > > (Sorry for being such a bureaucrat.) No problem, I overlooked that. > It's most appropriate in your 4/5 but do you think it'd be possible to > reshuffle the series to put the fix in front (to ease it for stable > kernels) and refactorings after? Let me give that a try. As it is right now, patches 1-3 are pre-reqs for 4. I can try to get the actual fix to the front and then add patches to additionally make nicer/refactor.