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[2604:1380:40f1:3f00::1]) by mx.google.com with ESMTPS id ci18-20020a17090afc9200b002a01941b7adsi2646896pjb.0.2024.03.21.17.47.55 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Mar 2024 17:47:56 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel+bounces-110834-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1; Authentication-Results: mx.google.com; dkim=pass header.i=@linux-foundation.org header.s=korg header.b="0jq/9Qyq"; arc=pass (i=1 dkim=pass dkdomain=linux-foundation.org); spf=pass (google.com: domain of linux-kernel+bounces-110834-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-110834-linux.lists.archive=gmail.com@vger.kernel.org" Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sy.mirrors.kernel.org (Postfix) with ESMTPS id 985A0B222AC for ; Fri, 22 Mar 2024 00:47:52 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id E305A818; Fri, 22 Mar 2024 00:47:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="0jq/9Qyq" 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 12481376 for ; Fri, 22 Mar 2024 00:47:43 +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=1711068464; cv=none; b=rmPvxgaZIxZp99s4vzeWh3hov2bjPba7FhzMNOpQ1Hx4FD1I5xJthtdXtU7ywEgrIgktM2tFGo2NExKyDLHxX2jKFDIMBQOtygNHXkWm4OiP++FMPT/bJIIRZMcqHIcqm9S40QPd570w5np8eM5BMbIrTtNIhluFAprHDeU8HRQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711068464; c=relaxed/simple; bh=7jVrCeB8r4Jhz+Oth0tMnxg2wwc/cCnXPK5b+noYuzI=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=mE8YDZ1BhHda+vYYnw44BrhDWdSJoOJCU43xbtwVA0jv97DKbyUMrUwnxHfGFxusvIZ4iGga6I7JD2PH22w7CB9UbFh0hyS4WHCKH6gYT2AHh6EiTrVe6BGtUdoQmYFC7BpDt+H7R7JYWdhHnmXwTLZMLM6i7zgpBgIG/p/Mjko= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=0jq/9Qyq; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 19590C433C7; Fri, 22 Mar 2024 00:47:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1711068463; bh=7jVrCeB8r4Jhz+Oth0tMnxg2wwc/cCnXPK5b+noYuzI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=0jq/9Qyqvev3SfPJwJcvNW8LTEnzWab/6cRd9shWI9urOkdwxu1yIruaSExNiafPd Fpqz4beoIGVnXN+QIEEUJmWPIPi/yUmQP0SnWn7pTVyxu4nGyQnMc3vt35dPxmDbWq sOhqhI0EDjZzkff2mD4D7gij31/aq/uSc8+hArEo= Date: Thu, 21 Mar 2024 17:47:42 -0700 From: Andrew Morton To: Lokesh Gidra Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, surenb@google.com, kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com, david@redhat.com, axelrasmussen@google.com, bgeffon@google.com, jannh@google.com, kaleshsingh@google.com, ngeoffray@google.com, rppt@kernel.org, hdanton@sina.com, syzbot+49056626fe41e01f2ba7@syzkaller.appspotmail.com Subject: Re: [PATCH] userfaultfd: fix deadlock warning when locking src and dst VMAs Message-Id: <20240321174742.6c5622f4406673629e266db7@linux-foundation.org> In-Reply-To: <20240321235818.125118-1-lokeshgidra@google.com> References: <20240321235818.125118-1-lokeshgidra@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 21 Mar 2024 16:58:18 -0700 Lokesh Gidra wrote: > Use down_read_nested() to avoid the warning. > > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -1444,7 +1444,8 @@ static int uffd_move_lock(struct mm_struct *mm, > */ > down_read(&(*dst_vmap)->vm_lock->lock); > if (*dst_vmap != *src_vmap) > - down_read(&(*src_vmap)->vm_lock->lock); > + down_read_nested(&(*src_vmap)->vm_lock->lock, > + SINGLE_DEPTH_NESTING); > } > mmap_read_unlock(mm); > return err; Thanks, I added Fixes: 867a43a34ff8a ("userfaultfd: use per-vma locks in userfaultfd operations")