From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751923AbdJ3Em1 (ORCPT ); Mon, 30 Oct 2017 00:42:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:57362 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751199AbdJ3Em0 (ORCPT ); Mon, 30 Oct 2017 00:42:26 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C07E021925 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=mhiramat@kernel.org Date: Mon, 30 Oct 2017 13:42:21 +0900 From: Masami Hiramatsu To: Bixuan Cui Cc: , "Libin (Huawei)" , "kangwen (A)" , "Leizhen (ThunderTown)" , , , , Subject: Re: [PATCH] kernel/kprobes: add check to avoid memory leaks Message-Id: <20171030134221.b2c17e36d4deb78a431a0067@kernel.org> In-Reply-To: <59F67C21.7020806@huawei.com> References: <59F08398.3020707@huawei.com> <59F67C21.7020806@huawei.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 30 Oct 2017 09:10:57 +0800 Bixuan Cui wrote: > On 2017/10/25 20:29, Bixuan Cui wrote: > And test again with this patch: > > insmod testRegKretprobes_004.ko > [ 163.853281] register_kretprobe failed, returned -22 > insmod: can't insert 'testRegKretprobes_004.ko': Operation not permitted > > Thanks, > Bixuan Cui > > The register_kretprobe(struct kretprobe *rp) creates and initializes > > a hash list for rp->free_instances when register kretprobe every time. > > Then malloc memory for it. > > > > The test case: > > static struct kretprobe rp; > > struct kretprobe *rps[2]={&rp, &rp}; > > static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs) > > { > > printk(KERN_DEBUG "ret_handler\n"); > > return 0; > > } > > static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs) > > { > > printk(KERN_DEBUG "entry_handler\n"); > > return 0; > > } > > static int __init kretprobe_init(void) > > { > > int ret; > > rp.kp.addr = (kprobe_opcode_t *)kallsyms_lookup_name("do_fork"); > > rp.handler=ret_handler; > > rp.entry_handler=entry_handler; > > rp.maxactive = 3; > > > > ret = register_kretprobes(rps,2); > > > > Result: > > unreferenced object 0xffff8010b12ad980 (size 64): > > comm "insmod", pid 17352, jiffies 4298977824 (age 63065.756s) > > hex dump (first 32 bytes): > > 00 00 00 00 00 00 00 00 d8 84 12 fc ff 7f ff ff ................ > > 74 65 73 74 52 65 67 4b 72 65 74 70 72 6f 62 65 testRegKretprobe > > backtrace: > > [] create_object+0x1e0/0x3f0 > > [] kmemleak_alloc+0x6c/0xf0 > > [] __kmalloc+0x23c/0x2e0 > > [] register_kretprobe+0x12c/0x350 > > > > When call register_kretprobes(struct kretprobe **rps, int num) with the > > same rps(num>=2). > > The first time,call INIT_HLIST_HEAD() and kmalloc() to malloc memory for the > > hash list,then save into rp->free_instances. > > The second time,call INIT_HLIST_HEAD() and kmalloc() then create a new > > hash list into rp->free_instances and lost the first rp->free_instances. > > So add check to avoid it. > > I don't like this kind of check, since this is obviously caller's bug. Why doesn't each caller check this? Thank you, > > Reported-and-tested-by: kangwen > > Signed-off-by: Bixuan Cui > > --- > > kernel/kprobes.c | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > index 6301dae..f19f191 100644 > > --- a/kernel/kprobes.c > > +++ b/kernel/kprobes.c > > @@ -1890,10 +1890,16 @@ EXPORT_SYMBOL_GPL(register_kretprobe); > > > > int register_kretprobes(struct kretprobe **rps, int num) > > { > > - int ret = 0, i; > > + int ret = 0, i, j; > > > > if (num <= 0) > > return -EINVAL; > > + > > + for (i = 0; i < num-1; i++) > > + for (j = i+1; j < num; j++) > > + if (rps[i] == rps[j]) > > + return -EINVAL; > > + > > for (i = 0; i < num; i++) { > > ret = register_kretprobe(rps[i]); > > if (ret < 0) { > > -- > > 2.6.2 > > > > > > > > > > . > > > > -- Masami Hiramatsu