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 10AD3ECAAA4 for ; Mon, 29 Aug 2022 17:50:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230047AbiH2RuX (ORCPT ); Mon, 29 Aug 2022 13:50:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56438 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230029AbiH2RuT (ORCPT ); Mon, 29 Aug 2022 13:50:19 -0400 Received: from smtp-fw-80006.amazon.com (smtp-fw-80006.amazon.com [99.78.197.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8FD5B25EB6 for ; Mon, 29 Aug 2022 10:50:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1661795417; x=1693331417; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=doEtQpNLhVe9LzFu3Vgaaur/sI+yQ3XzlBUFA2WhErc=; b=q2WMogZ3c/lC4XtD5uDhRUNtAHmvNsou3k5ld5zu3qoOxDQtpnAHpQBi CiZLiounahEmXHBY0JpVxKsRx7LKbrFwgCYONplDuYW3P8mIGGRKU9d1W QuwZZHARmeF4DXjSK0mvHmbyEUSWfDmp+HfatbUTOZOW+VpKNVYzh3ZSR w=; X-IronPort-AV: E=Sophos;i="5.93,273,1654560000"; d="scan'208";a="124451371" Received: from pdx4-co-svc-p1-lb2-vlan2.amazon.com (HELO email-inbound-relay-pdx-2b-1f9d5b26.us-west-2.amazon.com) ([10.25.36.210]) by smtp-border-fw-80006.pdx80.corp.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Aug 2022 17:49:58 +0000 Received: from EX13MTAUWB001.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan3.pdx.amazon.com [10.236.137.198]) by email-inbound-relay-pdx-2b-1f9d5b26.us-west-2.amazon.com (Postfix) with ESMTPS id 8550D419FD; Mon, 29 Aug 2022 17:49:56 +0000 (UTC) Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX13MTAUWB001.ant.amazon.com (10.43.161.207) with Microsoft SMTP Server (TLS) id 15.0.1497.38; Mon, 29 Aug 2022 17:49:55 +0000 Received: from 88665a182662.ant.amazon.com.com (10.43.160.191) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1118.12; Mon, 29 Aug 2022 17:49:53 +0000 From: Kuniyuki Iwashima To: CC: , , , , , , , Subject: [PATCH v3] seccomp: Move copy_seccomp() to no failure path. Date: Mon, 29 Aug 2022 10:49:45 -0700 Message-ID: <20220829174945.4398-1-kuniyu@amazon.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220823154532.82913-1-kuniyu@amazon.com> References: <20220823154532.82913-1-kuniyu@amazon.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.43.160.191] X-ClientProxiedBy: EX13D40UWA004.ant.amazon.com (10.43.160.36) To EX19D004ANA001.ant.amazon.com (10.37.240.138) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Kees, Could you take a look at this? Thank you. From: Kuniyuki Iwashima Date: Tue, 23 Aug 2022 08:45:32 -0700 > Our syzbot instance reported memory leaks in do_seccomp() [0], similar > to the report [1]. It shows that we miss freeing struct seccomp_filter > and some objects included in it. > > We can reproduce the issue with the program below [2] which calls one > seccomp() and two clone() syscalls. > > The first clone()d child exits earlier than its parent and sends a > signal to kill it during the second clone(), more precisely before the > fatal_signal_pending() test in copy_process(). When the parent receives > the signal, it has to destroy the embryonic process and return -EINTR to > user space. In the failure path, we have to call seccomp_filter_release() > to decrement the filter's refcount. > > Initially, we called it in free_task() called from the failure path, but > the commit 3a15fb6ed92c ("seccomp: release filter after task is fully > dead") moved it to release_task() to notify user space as early as possible > that the filter is no longer used. > > To keep the change and current seccomp refcount semantics, let's move > copy_seccomp() just after the signal check and add a WARN_ON_ONCE() in > free_task() for future debugging. > > [0]: > unreferenced object 0xffff8880063add00 (size 256): > comm "repro_seccomp", pid 230, jiffies 4294687090 (age 9.914s) > hex dump (first 32 bytes): > 01 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 ................ > ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................ > backtrace: > do_seccomp (./include/linux/slab.h:600 ./include/linux/slab.h:733 kernel/seccomp.c:666 kernel/seccomp.c:708 kernel/seccomp.c:1871 kernel/seccomp.c:1991) > do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) > entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) > unreferenced object 0xffffc90000035000 (size 4096): > comm "repro_seccomp", pid 230, jiffies 4294687090 (age 9.915s) > hex dump (first 32 bytes): > 01 00 00 00 00 00 00 00 00 00 00 00 05 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > backtrace: > __vmalloc_node_range (mm/vmalloc.c:3226) > __vmalloc_node (mm/vmalloc.c:3261 (discriminator 4)) > bpf_prog_alloc_no_stats (kernel/bpf/core.c:91) > bpf_prog_alloc (kernel/bpf/core.c:129) > bpf_prog_create_from_user (net/core/filter.c:1414) > do_seccomp (kernel/seccomp.c:671 kernel/seccomp.c:708 kernel/seccomp.c:1871 kernel/seccomp.c:1991) > do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) > entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) > unreferenced object 0xffff888003fa1000 (size 1024): > comm "repro_seccomp", pid 230, jiffies 4294687090 (age 9.915s) > hex dump (first 32 bytes): > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > backtrace: > bpf_prog_alloc_no_stats (./include/linux/slab.h:600 ./include/linux/slab.h:733 kernel/bpf/core.c:95) > bpf_prog_alloc (kernel/bpf/core.c:129) > bpf_prog_create_from_user (net/core/filter.c:1414) > do_seccomp (kernel/seccomp.c:671 kernel/seccomp.c:708 kernel/seccomp.c:1871 kernel/seccomp.c:1991) > do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) > entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) > unreferenced object 0xffff888006360240 (size 16): > comm "repro_seccomp", pid 230, jiffies 4294687090 (age 9.915s) > hex dump (first 16 bytes): > 01 00 37 00 76 65 72 6c e0 83 01 06 80 88 ff ff ..7.verl........ > backtrace: > bpf_prog_store_orig_filter (net/core/filter.c:1137) > bpf_prog_create_from_user (net/core/filter.c:1428) > do_seccomp (kernel/seccomp.c:671 kernel/seccomp.c:708 kernel/seccomp.c:1871 kernel/seccomp.c:1991) > do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) > entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) > unreferenced object 0xffff8880060183e0 (size 8): > comm "repro_seccomp", pid 230, jiffies 4294687090 (age 9.915s) > hex dump (first 8 bytes): > 06 00 00 00 00 00 ff 7f ........ > backtrace: > kmemdup (mm/util.c:129) > bpf_prog_store_orig_filter (net/core/filter.c:1144) > bpf_prog_create_from_user (net/core/filter.c:1428) > do_seccomp (kernel/seccomp.c:671 kernel/seccomp.c:708 kernel/seccomp.c:1871 kernel/seccomp.c:1991) > do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) > entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) > > [1]: https://syzkaller.appspot.com/bug?id=2809bb0ac77ad9aa3f4afe42d6a610aba594a987 > > [2]: > #define _GNU_SOURCE > #include > #include > #include > #include > #include > #include > > void main(void) > { > struct sock_filter filter[] = { > BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW), > }; > struct sock_fprog fprog = { > .len = sizeof(filter) / sizeof(filter[0]), > .filter = filter, > }; > long i, pid; > > syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER, 0, &fprog); > > for (i = 0; i < 2; i++) { > pid = syscall(__NR_clone, CLONE_NEWNET | SIGKILL, NULL, NULL, 0); > if (pid == 0) > return; > } > } > > Fixes: 3a15fb6ed92c ("seccomp: release filter after task is fully dead") > Reported-by: syzbot+ab17848fe269b573eb71@syzkaller.appspotmail.com > Reported-by: Ayushman Dutta > Suggested-by: Kees Cook > Signed-off-by: Kuniyuki Iwashima > Reviewed-by: Christian Brauner (Microsoft) > --- > v3: > * Fix build failure for CONFIG_SECCOMP=n case > > v2: https://lore.kernel.org/lkml/20220823004806.38681-1-kuniyu@amazon.com/ > * Move copy_seccomp() after no failure path instead of adding > seccomp_filter_release() in the failure path. > > v1: https://lore.kernel.org/lkml/20220822204436.26631-1-kuniyu@amazon.com/ > --- > kernel/fork.c | 17 +++++++++++------ > 1 file changed, 11 insertions(+), 6 deletions(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 90c85b17bf69..6ac1cc62f197 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -537,6 +537,9 @@ void put_task_stack(struct task_struct *tsk) > > void free_task(struct task_struct *tsk) > { > +#ifdef CONFIG_SECCOMP > + WARN_ON_ONCE(tsk->seccomp.filter); > +#endif > release_user_cpus_ptr(tsk); > scs_release(tsk); > > @@ -2409,12 +2412,6 @@ static __latent_entropy struct task_struct *copy_process( > > spin_lock(¤t->sighand->siglock); > > - /* > - * Copy seccomp details explicitly here, in case they were changed > - * before holding sighand lock. > - */ > - copy_seccomp(p); > - > rv_task_fork(p); > > rseq_fork(p, clone_flags); > @@ -2431,6 +2428,14 @@ static __latent_entropy struct task_struct *copy_process( > goto bad_fork_cancel_cgroup; > } > > + /* No more failure paths after this point. */ > + > + /* > + * Copy seccomp details explicitly here, in case they were changed > + * before holding sighand lock. > + */ > + copy_seccomp(p); > + > init_task_pid_links(p); > if (likely(p->pid)) { > ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); > -- > 2.30.2