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 X-Spam-Level: X-Spam-Status: No, score=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EAC8AC7618F for ; Fri, 19 Jul 2019 23:07:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE19C21873 for ; Fri, 19 Jul 2019 23:07:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563577676; bh=6h+e0DQ6omq60QcQu5YWlxGv1jSCpjt2R+a+Cp1vyTA=; h=Subject:From:To:Cc:Date:In-Reply-To:References:List-ID:From; b=osXda2Qynn3bP1cDnCXY2AsuC5AY+0tPZUtodtqI7JYm++GzrTDlFW8rjux77pk1C A6aDLA3orNLd9bi6Ob8CzImLLiz+rE17C37qJHllBJG32IwRBVMsN6lyzC2f6F554i DSyI0vbW0GHHVtlZOfM6mHuMYpJac3LPsx/GxvWM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732536AbfGSXHw (ORCPT ); Fri, 19 Jul 2019 19:07:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:45954 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728747AbfGSXHw (ORCPT ); Fri, 19 Jul 2019 19:07:52 -0400 Received: from tleilax.poochiereds.net (cpe-71-70-156-158.nc.res.rr.com [71.70.156.158]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6EB5C2089C; Fri, 19 Jul 2019 23:07:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563577671; bh=6h+e0DQ6omq60QcQu5YWlxGv1jSCpjt2R+a+Cp1vyTA=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=SVSCVAFUR7KijMhbggA2vVf9ja197HO3/EZeglfHS1uLj9MGTrj6TLon1iUEsoAbL jXwNqirqqO0t4OgBKa/kOxQEXzXZaavgFvHlW6hwkYV5Evp2/qYbEe+wjCVC+BM0cL OsgVjE2yQ+OoUdCFqwS8j2fC5vfL3LB82Eo0A8Qo= Message-ID: <1dee14212043f12ef5b26e4aee0c3155e118abf3.camel@kernel.org> Subject: Re: [PATCH 2/4] ceph: fix buffer free while holding i_ceph_lock in __ceph_setxattr() From: Jeff Layton To: Luis Henriques , Ilya Dryomov , Sage Weil Cc: ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org, Al Viro Date: Fri, 19 Jul 2019 19:07:49 -0400 In-Reply-To: <20190719143222.16058-3-lhenriques@suse.com> References: <20190719143222.16058-1-lhenriques@suse.com> <20190719143222.16058-3-lhenriques@suse.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.32.4 (3.32.4-1.fc30) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2019-07-19 at 15:32 +0100, Luis Henriques wrote: > Calling ceph_buffer_put() in __ceph_setxattr() may end up freeing the > i_xattrs.prealloc_blob buffer while holding the i_ceph_lock. This can be > fixed by postponing the call until later, when the lock is released. > > The following backtrace was triggered by fstests generic/117. > > BUG: sleeping function called from invalid context at mm/vmalloc.c:2283 > in_atomic(): 1, irqs_disabled(): 0, pid: 650, name: fsstress > 3 locks held by fsstress/650: > #0: 00000000870a0fe8 (sb_writers#8){.+.+}, at: mnt_want_write+0x20/0x50 > #1: 00000000ba0c4c74 (&type->i_mutex_dir_key#6){++++}, at: vfs_setxattr+0x55/0xa0 > #2: 000000008dfbb3f2 (&(&ci->i_ceph_lock)->rlock){+.+.}, at: __ceph_setxattr+0x297/0x810 > CPU: 1 PID: 650 Comm: fsstress Not tainted 5.2.0+ #437 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-prebuilt.qemu.org 04/01/2014 > Call Trace: > dump_stack+0x67/0x90 > ___might_sleep.cold+0x9f/0xb1 > vfree+0x4b/0x60 > ceph_buffer_release+0x1b/0x60 > __ceph_setxattr+0x2b4/0x810 > __vfs_setxattr+0x66/0x80 > __vfs_setxattr_noperm+0x59/0xf0 > vfs_setxattr+0x81/0xa0 > setxattr+0x115/0x230 > ? filename_lookup+0xc9/0x140 > ? rcu_read_lock_sched_held+0x74/0x80 > ? rcu_sync_lockdep_assert+0x2e/0x60 > ? __sb_start_write+0x142/0x1a0 > ? mnt_want_write+0x20/0x50 > path_setxattr+0xba/0xd0 > __x64_sys_lsetxattr+0x24/0x30 > do_syscall_64+0x50/0x1c0 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x7ff23514359a > > Signed-off-by: Luis Henriques > --- > fs/ceph/xattr.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c > index 37b458a9af3a..c083557b3657 100644 > --- a/fs/ceph/xattr.c > +++ b/fs/ceph/xattr.c > @@ -1036,6 +1036,7 @@ int __ceph_setxattr(struct inode *inode, const char *name, > struct ceph_inode_info *ci = ceph_inode(inode); > struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc; > struct ceph_cap_flush *prealloc_cf = NULL; > + struct ceph_buffer *old_blob = NULL; > int issued; > int err; > int dirty = 0; > @@ -1109,13 +1110,15 @@ int __ceph_setxattr(struct inode *inode, const char *name, > struct ceph_buffer *blob; > > spin_unlock(&ci->i_ceph_lock); > - dout(" preaallocating new blob size=%d\n", required_blob_size); > + ceph_buffer_put(old_blob); /* Shouldn't be required */ > + dout(" pre-allocating new blob size=%d\n", required_blob_size); > blob = ceph_buffer_new(required_blob_size, GFP_NOFS); > if (!blob) > goto do_sync_unlocked; > spin_lock(&ci->i_ceph_lock); > + /* prealloc_blob can't be released while holding i_ceph_lock */ > if (ci->i_xattrs.prealloc_blob) > - ceph_buffer_put(ci->i_xattrs.prealloc_blob); > + old_blob = ci->i_xattrs.prealloc_blob; > ci->i_xattrs.prealloc_blob = blob; > goto retry; > } > @@ -1131,6 +1134,7 @@ int __ceph_setxattr(struct inode *inode, const char *name, > } > > spin_unlock(&ci->i_ceph_lock); > + ceph_buffer_put(old_blob); > if (lock_snap_rwsem) > up_read(&mdsc->snap_rwsem); > if (dirty) (cc'ing Al) Al pointed out on IRC that vfree should be callable under spinlock. It only sleeps if !in_interrupt(), and I think that should return true if we're holding a spinlock. I'll plan to try replicating this soon. -- Jeff Layton