From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C1A8BC25B06 for ; Sat, 6 Aug 2022 07:45:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241742AbiHFHpD (ORCPT ); Sat, 6 Aug 2022 03:45:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43076 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241672AbiHFHo6 (ORCPT ); Sat, 6 Aug 2022 03:44:58 -0400 Received: from sender-of-o53.zoho.in (sender-of-o53.zoho.in [103.117.158.53]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 19A9911C35 for ; Sat, 6 Aug 2022 00:44:51 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1659771858; cv=none; d=zohomail.in; s=zohoarc; b=ZhewqxYZXZ+4d92N7/6+E+8roDitfj9snck27koQpePAE3WFuk9MjvSwIGz6eWGCFsV02NvYCyXgHjlcFYzpshrM4HYwvhhVFUEknCgVLTEyUrktXLIGER38MjWFJt4+UKcfvW/AQOzj2uYhK+wNJLTdvfB9NkK0w+PTsFa4FNU= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.in; s=zohoarc; t=1659771858; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:To; bh=CciC0JA+1Sl6P741HLOLO7oPE18KzPzTWUnJ9g4NcCY=; b=cThpGGll9oucn4GJNKQsynEm1XnwpouK/xSplDvh7EmGcmv1JQV1HiDQYNz1ZyKZF9/qgn0BLQvGxm4z1cPHh3yr4nThvtfxGzQNXC7Mp80DVRyKbCj/uO00qnfCIvwnYQPm/T6c0GvGRLUYueBru+KgtpLIi58OMt2Iq1eVe+E= ARC-Authentication-Results: i=1; mx.zohomail.in; dkim=pass header.i=siddh.me; spf=pass smtp.mailfrom=code@siddh.me; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1659771858; s=zmail; d=siddh.me; i=code@siddh.me; h=From:From:To:To:Cc:Cc:Message-ID:Subject:Subject:Date:Date:In-Reply-To:References:MIME-Version:Content-Transfer-Encoding:Content-Type:Message-Id:Reply-To; bh=CciC0JA+1Sl6P741HLOLO7oPE18KzPzTWUnJ9g4NcCY=; b=JM4WjGJ0hHN4JfmzzT4r8K6mAuU1dym79SIEZ/Y2OH3I+04GYX6u2zRwNNXlbves kQPJPG2nNPGEzXxrjpAKzpRvNKOc6foAddrDlVhbZngJ8XzVHTBEYCXhRKsbRLe+RlJ X+0l+Ky/Qt8f+EO+ucwhV9nwa+gC5+HS/vz8ZQJ0= Received: from localhost.localdomain (43.250.158.93 [43.250.158.93]) by mx.zoho.in with SMTPS id 165977185695375.74638919740744; Sat, 6 Aug 2022 13:14:16 +0530 (IST) From: Siddh Raman Pant To: Eric Biggers , Jonathan Corbet , David Howells , Randy Dunlap , Mauro Carvalho Chehab , Christophe JAILLET , Eric Dumazet Cc: linux-kernel , linux-kernel-mentees Message-ID: Subject: [PATCH v2 2/2] kernel/watch_queue: NULL the dangling *pipe, and use it for clear check Date: Sat, 6 Aug 2022 13:13:42 +0530 X-Mailer: git-send-email 2.35.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMailClient: External Content-Type: text/plain; charset=utf8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org NULL the dangling pipe reference while clearing watch_queue. If not done, a reference to a freed pipe remains in the watch_queue, as this function is called before freeing a pipe in free_pipe_info() (see line 834 of fs/pipe.c). The sole use of wqueue->defunct is for checking if the watch queue has been cleared, but wqueue->pipe is also NULLed while clearing. Thus, wqueue->defunct is superfluous, as wqueue->pipe can be checked for NULL. Hence, the former can be removed. Signed-off-by: Siddh Raman Pant --- include/linux/watch_queue.h | 4 +--- kernel/watch_queue.c | 12 ++++++------ 2 files changed, 7 insertions(+), 9 deletions(-) diff --git a/include/linux/watch_queue.h b/include/linux/watch_queue.h index 7f8b1f15634b..d72ad82a4435 100644 --- a/include/linux/watch_queue.h +++ b/include/linux/watch_queue.h @@ -55,7 +55,7 @@ struct watch_filter { * * @rcu: RCU head * @filter: Filter to use on watches - * @pipe: The pipe we're using as a buffer + * @pipe: The pipe we're using as a buffer, NULL when queue is cleared/clo= sed * @watches: Contributory watches * @notes: Preallocated notifications * @notes_bitmap: Allocation bitmap for notes @@ -63,7 +63,6 @@ struct watch_filter { * @lock: To serialize accesses and removes * @nr_notes: Number of notes * @nr_pages: Number of pages in notes[] - * @defunct: True when queues closed */ struct watch_queue { =09struct rcu_head=09=09rcu; @@ -76,7 +75,6 @@ struct watch_queue { =09spinlock_t=09=09lock; =09unsigned int=09=09nr_notes; =09unsigned int=09=09nr_pages; -=09bool=09=09=09defunct; }; =20 /** diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c index a6f9bdd956c3..a70ddfd622ee 100644 --- a/kernel/watch_queue.c +++ b/kernel/watch_queue.c @@ -43,7 +43,7 @@ MODULE_LICENSE("GPL"); static inline bool lock_wqueue(struct watch_queue *wqueue) { =09spin_lock_bh(&wqueue->lock); -=09if (unlikely(wqueue->defunct)) { +=09if (unlikely(!wqueue->pipe)) { =09=09spin_unlock_bh(&wqueue->lock); =09=09return false; =09} @@ -105,9 +105,6 @@ static bool post_one_notification(struct watch_queue *w= queue, =09unsigned int head, tail, mask, note, offset, len; =09bool done =3D false; =20 -=09if (!pipe) -=09=09return false; - =09spin_lock_irq(&pipe->rd_wait.lock); =20 =09mask =3D pipe->ring_size - 1; @@ -603,8 +600,11 @@ void watch_queue_clear(struct watch_queue *wqueue) =09rcu_read_lock(); =09spin_lock_bh(&wqueue->lock); =20 -=09/* Prevent new notifications from being stored. */ -=09wqueue->defunct =3D true; +=09/* +=09 * This pipe will get freed by the caller free_pipe_info(). +=09 * Removing this reference also prevents new notifications. +=09 */ +=09wqueue->pipe =3D NULL; =20 =09while (!hlist_empty(&wqueue->watches)) { =09=09watch =3D hlist_entry(wqueue->watches.first, struct watch, queue_nod= e); --=20 2.35.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF12DECAAD2 for ; Thu, 1 Sep 2022 20:08:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234836AbiIAUIF (ORCPT ); Thu, 1 Sep 2022 16:08:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37946 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232332AbiIAUHw (ORCPT ); Thu, 1 Sep 2022 16:07:52 -0400 Received: from sender-of-o50.zoho.in (sender-of-o50.zoho.in [103.117.158.50]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E5B2199B75 for ; Thu, 1 Sep 2022 13:07:49 -0700 (PDT) ARC-Seal: i=1; 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bh=CciC0JA+1Sl6P741HLOLO7oPE18KzPzTWUnJ9g4NcCY=; b=hoDe65BsScmByWk2StwOsdECPhjE7FCJHqIBQbIlA7jZyet6KkAqAq3g8shZNgJx Nqh1hewTv79nBw+yAP43BnBLL71G+YgJeDhW/BupTrfRNKtVBqRLhdNNg7PBQiEv9Zf uktufTpEscH3cMdVxWMV8o9nfp6aBDto+97ZZ8KM= Received: from localhost.localdomain (103.249.233.18 [103.249.233.18]) by mx.zoho.in with SMTPS id 1662062827191296.66769203214255; Fri, 2 Sep 2022 01:37:07 +0530 (IST) From: Siddh Raman Pant To: Jonathan Corbet , David Howells , Randy Dunlap , Mauro Carvalho Chehab , Christophe JAILLET , Eric Dumazet , Eric Biggers Cc: linux-kernel , linux-kernel-mentees Message-ID: Subject: [RESEND PATCH v2 2/2] kernel/watch_queue: NULL the dangling *pipe, and use it for clear check Date: Fri, 2 Sep 2022 01:36:56 +0530 X-Mailer: git-send-email 2.35.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMailClient: External Content-Type: text/plain; charset=utf8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Message-ID: <20220901200656.7s0LRBimw09DxwvR6S_XuwWkyzJA8UmKe8UJP4vlr2k@z> NULL the dangling pipe reference while clearing watch_queue. If not done, a reference to a freed pipe remains in the watch_queue, as this function is called before freeing a pipe in free_pipe_info() (see line 834 of fs/pipe.c). The sole use of wqueue->defunct is for checking if the watch queue has been cleared, but wqueue->pipe is also NULLed while clearing. Thus, wqueue->defunct is superfluous, as wqueue->pipe can be checked for NULL. Hence, the former can be removed. Signed-off-by: Siddh Raman Pant --- include/linux/watch_queue.h | 4 +--- kernel/watch_queue.c | 12 ++++++------ 2 files changed, 7 insertions(+), 9 deletions(-) diff --git a/include/linux/watch_queue.h b/include/linux/watch_queue.h index 7f8b1f15634b..d72ad82a4435 100644 --- a/include/linux/watch_queue.h +++ b/include/linux/watch_queue.h @@ -55,7 +55,7 @@ struct watch_filter { * * @rcu: RCU head * @filter: Filter to use on watches - * @pipe: The pipe we're using as a buffer + * @pipe: The pipe we're using as a buffer, NULL when queue is cleared/clo= sed * @watches: Contributory watches * @notes: Preallocated notifications * @notes_bitmap: Allocation bitmap for notes @@ -63,7 +63,6 @@ struct watch_filter { * @lock: To serialize accesses and removes * @nr_notes: Number of notes * @nr_pages: Number of pages in notes[] - * @defunct: True when queues closed */ struct watch_queue { =09struct rcu_head=09=09rcu; @@ -76,7 +75,6 @@ struct watch_queue { =09spinlock_t=09=09lock; =09unsigned int=09=09nr_notes; =09unsigned int=09=09nr_pages; -=09bool=09=09=09defunct; }; =20 /** diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c index a6f9bdd956c3..a70ddfd622ee 100644 --- a/kernel/watch_queue.c +++ b/kernel/watch_queue.c @@ -43,7 +43,7 @@ MODULE_LICENSE("GPL"); static inline bool lock_wqueue(struct watch_queue *wqueue) { =09spin_lock_bh(&wqueue->lock); -=09if (unlikely(wqueue->defunct)) { +=09if (unlikely(!wqueue->pipe)) { =09=09spin_unlock_bh(&wqueue->lock); =09=09return false; =09} @@ -105,9 +105,6 @@ static bool post_one_notification(struct watch_queue *w= queue, =09unsigned int head, tail, mask, note, offset, len; =09bool done =3D false; =20 -=09if (!pipe) -=09=09return false; - =09spin_lock_irq(&pipe->rd_wait.lock); =20 =09mask =3D pipe->ring_size - 1; @@ -603,8 +600,11 @@ void watch_queue_clear(struct watch_queue *wqueue) =09rcu_read_lock(); =09spin_lock_bh(&wqueue->lock); =20 -=09/* Prevent new notifications from being stored. */ -=09wqueue->defunct =3D true; +=09/* +=09 * This pipe will get freed by the caller free_pipe_info(). +=09 * Removing this reference also prevents new notifications. +=09 */ +=09wqueue->pipe =3D NULL; =20 =09while (!hlist_empty(&wqueue->watches)) { =09=09watch =3D hlist_entry(wqueue->watches.first, struct watch, queue_nod= e); --=20 2.35.1