From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out1-smtp.messagingengine.com ([66.111.4.25]:59853 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726203AbeLKOAN (ORCPT ); Tue, 11 Dec 2018 09:00:13 -0500 Subject: FAILED: patch "[PATCH] dax: Don't access a freed inode" failed to apply to 4.19-stable tree To: willy@infradead.org, dan.j.williams@intel.com, jack@suse.cz, stable@vger.kernel.org Cc: From: Date: Tue, 11 Dec 2018 15:00:09 +0100 Message-ID: <1544536809243247@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >>From 55e56f06ed71d9441f3abd5b1d3c1a870812b3fe Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Tue, 27 Nov 2018 13:16:34 -0800 Subject: [PATCH] dax: Don't access a freed inode After we drop the i_pages lock, the inode can be freed at any time. The get_unlocked_entry() code has no choice but to reacquire the lock, so it can't be used here. Create a new wait_entry_unlocked() which takes care not to acquire the lock or dereference the address_space in any way. Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()") Cc: Signed-off-by: Matthew Wilcox Reviewed-by: Jan Kara Signed-off-by: Dan Williams diff --git a/fs/dax.c b/fs/dax.c index e69fc231833b..3f592dc18d67 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -232,6 +232,34 @@ static void *get_unlocked_entry(struct xa_state *xas) } } +/* + * The only thing keeping the address space around is the i_pages lock + * (it's cycled in clear_inode() after removing the entries from i_pages) + * After we call xas_unlock_irq(), we cannot touch xas->xa. + */ +static void wait_entry_unlocked(struct xa_state *xas, void *entry) +{ + struct wait_exceptional_entry_queue ewait; + wait_queue_head_t *wq; + + init_wait(&ewait.wait); + ewait.wait.func = wake_exceptional_entry_func; + + wq = dax_entry_waitqueue(xas, entry, &ewait.key); + prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE); + xas_unlock_irq(xas); + schedule(); + finish_wait(wq, &ewait.wait); + + /* + * Entry lock waits are exclusive. Wake up the next waiter since + * we aren't sure we will acquire the entry lock and thus wake + * the next waiter up on unlock. + */ + if (waitqueue_active(wq)) + __wake_up(wq, TASK_NORMAL, 1, &ewait.key); +} + static void put_unlocked_entry(struct xa_state *xas, void *entry) { /* If we were the only waiter woken, wake the next one */ @@ -389,9 +417,7 @@ bool dax_lock_mapping_entry(struct page *page) entry = xas_load(&xas); if (dax_is_locked(entry)) { rcu_read_unlock(); - entry = get_unlocked_entry(&xas); - xas_unlock_irq(&xas); - put_unlocked_entry(&xas, entry); + wait_entry_unlocked(&xas, entry); rcu_read_lock(); continue; }