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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 822DAC2D0E8 for ; Fri, 3 Apr 2020 09:37:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5B7B6208E4 for ; Fri, 3 Apr 2020 09:37:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390432AbgDCJhF (ORCPT ); Fri, 3 Apr 2020 05:37:05 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:47143 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727843AbgDCJhF (ORCPT ); Fri, 3 Apr 2020 05:37:05 -0400 Received: from ip5f5bf7ec.dynamic.kabel-deutschland.de ([95.91.247.236] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jKIkI-0000BB-CT; Fri, 03 Apr 2020 09:36:14 +0000 Date: Fri, 3 Apr 2020 11:36:12 +0200 From: Christian Brauner To: Oleg Nesterov Cc: syzbot , adobriyan@gmail.com, akpm@linux-foundation.org, allison@lohutok.net, areber@redhat.com, aubrey.li@linux.intel.com, avagin@gmail.com, bfields@fieldses.org, christian@brauner.io, cyphar@cyphar.com, ebiederm@xmission.com, gregkh@linuxfoundation.org, guro@fb.com, jlayton@kernel.org, joel@joelfernandes.org, keescook@chromium.org, linmiaohe@huawei.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, mhocko@suse.com, mingo@kernel.org, peterz@infradead.org, sargun@sargun.me, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, viro@zeniv.linux.org.uk Subject: Re: possible deadlock in send_sigurg Message-ID: <20200403093612.mtd7edubsng24uuh@wittgenstein> References: <00000000000011d66805a25cd73f@google.com> <20200403091135.GA3645@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200403091135.GA3645@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 03, 2020 at 11:11:35AM +0200, Oleg Nesterov wrote: > On 04/02, syzbot wrote: > > > > lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923 > > __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] > > _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151 > > spin_lock include/linux/spinlock.h:353 [inline] > > proc_pid_make_inode+0x1f9/0x3c0 fs/proc/base.c:1880 > > Yes, spin_lock(wait_pidfd.lock) is not safe... > > Eric, at first glance the fix is simple. > > Oleg. > > > diff --git a/fs/proc/base.c b/fs/proc/base.c Um, when did this lock get added to proc/base.c in the first place and why has it been abused for this? People just recently complained loudly about this in the cred_guard_mutex thread that abusing locks for things they weren't intended for is a bad idea... > index 74f948a6b621..9ec8c114aa60 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -1839,9 +1839,9 @@ void proc_pid_evict_inode(struct proc_inode *ei) > struct pid *pid = ei->pid; > > if (S_ISDIR(ei->vfs_inode.i_mode)) { > - spin_lock(&pid->wait_pidfd.lock); > + spin_lock_irq(&pid->wait_pidfd.lock); > hlist_del_init_rcu(&ei->sibling_inodes); > - spin_unlock(&pid->wait_pidfd.lock); > + spin_unlock_irq(&pid->wait_pidfd.lock); > } > > put_pid(pid); > @@ -1877,9 +1877,9 @@ struct inode *proc_pid_make_inode(struct super_block * sb, > /* Let the pid remember us for quick removal */ > ei->pid = pid; > if (S_ISDIR(mode)) { > - spin_lock(&pid->wait_pidfd.lock); > + spin_lock_irq(&pid->wait_pidfd.lock); > hlist_add_head_rcu(&ei->sibling_inodes, &pid->inodes); > - spin_unlock(&pid->wait_pidfd.lock); > + spin_unlock_irq(&pid->wait_pidfd.lock); > } > > task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid); > diff --git a/fs/proc/inode.c b/fs/proc/inode.c > index 1e730ea1dcd6..6b7ee76e1b36 100644 > --- a/fs/proc/inode.c > +++ b/fs/proc/inode.c > @@ -123,9 +123,9 @@ void proc_invalidate_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock > if (!node) > break; > ei = hlist_entry(node, struct proc_inode, sibling_inodes); > - spin_lock(lock); > + spin_lock_irq(lock); > hlist_del_init_rcu(&ei->sibling_inodes); > - spin_unlock(lock); > + spin_unlock_irq(lock); > > inode = &ei->vfs_inode; > sb = inode->i_sb; >