From patchwork Tue Apr 26 08:21:22 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 567858 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 B5E43C35280 for ; Tue, 26 Apr 2022 08:58:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343651AbiDZI5r (ORCPT ); Tue, 26 Apr 2022 04:57:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57810 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346040AbiDZIoe (ORCPT ); Tue, 26 Apr 2022 04:44:34 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF2601606BF; Tue, 26 Apr 2022 01:34:07 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D2FC4B81D0B; Tue, 26 Apr 2022 08:34:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 43817C385AF; Tue, 26 Apr 2022 08:34:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1650962044; bh=MloYW9hWeVoGLvgwUKtBkfZ0MZsDwu3/pbcTqCOAJVw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Y0RjSi8+qBJwVM1gDY6yFh/v8z8zfLorNfd3qkgkKgd5ihbZUmpwbFj0vP3DuuO1+ QXOhryNWb1Qq7j6o5E6oSVairOHLWX2hNbFjuHuUdcmNdnC0DUrR1LAuLKnq1G3CkN PhEpdTQWLI+JNe2uXwUHmFjciHGURDlaL+o6Sr7o= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alistair Popple , Jason Gunthorpe , =?utf-8?q?Christian_K=C3=B6nig?= , John Hubbard , Ralph Campbell , Andrew Morton , Linus Torvalds Subject: [PATCH 5.10 54/86] mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove() Date: Tue, 26 Apr 2022 10:21:22 +0200 Message-Id: <20220426081742.764495905@linuxfoundation.org> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220426081741.202366502@linuxfoundation.org> References: <20220426081741.202366502@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Alistair Popple commit 319561669a59d8e9206ab311ae5433ef92fd79d1 upstream. In some cases it is possible for mmu_interval_notifier_remove() to race with mn_tree_inv_end() allowing it to return while the notifier data structure is still in use. Consider the following sequence: CPU0 - mn_tree_inv_end() CPU1 - mmu_interval_notifier_remove() ----------------------------------- ------------------------------------ spin_lock(subscriptions->lock); seq = subscriptions->invalidate_seq; spin_lock(subscriptions->lock); spin_unlock(subscriptions->lock); subscriptions->invalidate_seq++; wait_event(invalidate_seq != seq); return; interval_tree_remove(interval_sub); kfree(interval_sub); spin_unlock(subscriptions->lock); wake_up_all(); As the wait_event() condition is true it will return immediately. This can lead to use-after-free type errors if the caller frees the data structure containing the interval notifier subscription while it is still on a deferred list. Fix this by taking the appropriate lock when reading invalidate_seq to ensure proper synchronisation. I observed this whilst running stress testing during some development. You do have to be pretty unlucky, but it leads to the usual problems of use-after-free (memory corruption, kernel crash, difficult to diagnose WARN_ON, etc). Link: https://lkml.kernel.org/r/20220420043734.476348-1-apopple@nvidia.com Fixes: 99cb252f5e68 ("mm/mmu_notifier: add an interval tree notifier") Signed-off-by: Alistair Popple Signed-off-by: Jason Gunthorpe Cc: Christian König Cc: John Hubbard Cc: Ralph Campbell Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/mmu_notifier.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) --- a/mm/mmu_notifier.c +++ b/mm/mmu_notifier.c @@ -1043,6 +1043,18 @@ int mmu_interval_notifier_insert_locked( } EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert_locked); +static bool +mmu_interval_seq_released(struct mmu_notifier_subscriptions *subscriptions, + unsigned long seq) +{ + bool ret; + + spin_lock(&subscriptions->lock); + ret = subscriptions->invalidate_seq != seq; + spin_unlock(&subscriptions->lock); + return ret; +} + /** * mmu_interval_notifier_remove - Remove a interval notifier * @interval_sub: Interval subscription to unregister @@ -1090,7 +1102,7 @@ void mmu_interval_notifier_remove(struct lock_map_release(&__mmu_notifier_invalidate_range_start_map); if (seq) wait_event(subscriptions->wq, - READ_ONCE(subscriptions->invalidate_seq) != seq); + mmu_interval_seq_released(subscriptions, seq)); /* pairs with mmgrab in mmu_interval_notifier_insert() */ mmdrop(mm);