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bh=iPgK2kOckPrF6unVEy275h6GDVcw1kRGlfXOTst5ZVU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NOvAnDj6uwG3zv+/jw9mhedjmVjiRMDTTpEyyjbs2B+tSyu7hIIyugZ6KkBcT8Ok7 IB9AaOVV6ozNS8YNlfaoL3Seeq0+1L4g0SD1+WqKuS1zHrudhTwcwpQadO6e8V2P5b YNwypio5hR9fQr+yNi3v2LkaFWlCjXaYVLxnRRM0= Date: Thu, 30 Mar 2023 12:42:30 -0700 From: Andrew Morton To: Mathieu Desnoyers Cc: linux-kernel@vger.kernel.org, Shakeel Butt , Marek Szyprowski , linux-mm@kvack.org, stable@vger.kernel.org Subject: Re: [PATCH 1/1] mm: Fix memory leak on mm_init error handling Message-Id: <20230330124230.9f3d4f63374eb15a3b990ff8@linux-foundation.org> In-Reply-To: <20230330133822.66271-1-mathieu.desnoyers@efficios.com> References: <20230330133822.66271-1-mathieu.desnoyers@efficios.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 6FBFE4000B X-Stat-Signature: fc9smq3u3pe9eajgm3eqduseuwqa7xz5 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1680205354-841572 X-HE-Meta: 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 SJasIOYg DaWsZ+7CTzA7+Qcy4nIxvHvsSwv6UycXy8GZmERiqU9YJ47t/QzqgcEjVl4uiibGBVcX7RY05hYskX6wRjk73mvAvt6C9OECTv6SeR9mMPGWYP5e0Z1sTPzEU7E4WrYZ28aWoShkhEjK4DkNZ0cppIKdtIYrUU5NcgzWuLX4qDpOmp/bFeBwD9RPx2g/kXKGz8vwDRqOIaA+k/YVRHFsYTKR1GLv7UpJ5eKrG1OoUolSm8IZsBiJLeki4HJi3rOSYoz/fPi5HuBLOTQcl5INhOd7t3w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 30 Mar 2023 09:38:22 -0400 Mathieu Desnoyers wrote: > commit f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter") > introduces a memory leak by missing a call to destroy_context() when a > percpu_counter fails to allocate. > > Before introducing the per-cpu counter allocations, init_new_context() > was the last call that could fail in mm_init(), and thus there was no > need to ever invoke destroy_context() in the error paths. Adding the > following percpu counter allocations adds error paths after > init_new_context(), which means its associated destroy_context() needs > to be called when percpu counters fail to allocate. > > ... > > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1171,6 +1171,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, > fail_pcpu: > while (i > 0) > percpu_counter_destroy(&mm->rss_stat[--i]); > + destroy_context(mm); > fail_nocontext: > mm_free_pgd(mm); > fail_nopgd: Is there really a leak? I wasn't able to find a version of init_new_context() which performs allocation.