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[195.135.220.15]) by mx.google.com with ESMTPS id t24si2122173edd.357.2019.06.10.06.58.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 10 Jun 2019 06:58:24 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 2EFEDABD2; Mon, 10 Jun 2019 13:58:24 +0000 (UTC) Date: Mon, 10 Jun 2019 15:58:23 +0200 From: Michal Hocko To: Stable tree Cc: Greg KH , linux-mm@kvack.org, LKML , Andrea Arcangeli , Jann Horn , Oleg Nesterov , Peter Xu , Mike Rapoport , Jason Gunthorpe , Andrew Morton , Linus Torvalds , Joel Fernandes Subject: Re: [PATCH stable 4.4 v2] coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping Message-ID: <20190610135823.GI30967@dhcp22.suse.cz> References: <20190604094953.26688-1-mhocko@kernel.org> <20190610074635.2319-1-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190610074635.2319-1-mhocko@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) 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: Just a heads up. Ajay Kaher has noticed that mlx4 driver is missing the check in 4.14 [1] and 4.4 seems to have the same problem. I will wait for more review before reposting v3. The incremental diff is: diff --git a/drivers/infiniband/hw/mlx4/main.c b/drivers/infiniband/hw/mlx4/main.c index 67c4c73343d4..6968154a073e 100644 --- a/drivers/infiniband/hw/mlx4/main.c +++ b/drivers/infiniband/hw/mlx4/main.c @@ -1042,6 +1042,8 @@ static void mlx4_ib_disassociate_ucontext(struct ib_ucontext *ibcontext) * mlx4_ib_vma_close(). */ down_write(&owning_mm->mmap_sem); + if (!mmget_still_valid(owning_mm)) + goto skip_mm; for (i = 0; i < HW_BAR_COUNT; i++) { vma = context->hw_bar_info[i].vma; if (!vma) @@ -1061,6 +1063,7 @@ static void mlx4_ib_disassociate_ucontext(struct ib_ucontext *ibcontext) context->hw_bar_info[i].vma->vm_ops = NULL; } +skip_mm: up_write(&owning_mm->mmap_sem); mmput(owning_mm); put_task_struct(owning_process); -- Michal Hocko SUSE Labs