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Date: Sat, 10 Dec 2022 13:29:22 -0800 From: Cong Wang <xiyou.wangcong@...il.com> To: Hawkins Jiawei <yin31149@...il.com> Cc: 18801353760@....com, cong.wang@...edance.com, davem@...emloft.net, dvyukov@...gle.com, edumazet@...gle.com, jhs@...atatu.com, jiri@...nulli.us, kuba@...nel.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, pabeni@...hat.com, syzbot+232ebdbd36706c965ebf@...kaller.appspotmail.com, syzkaller-bugs@...glegroups.com Subject: Re: [PATCH v3] net: sched: fix memory leak in tcindex_set_parms On Mon, Dec 05, 2022 at 11:19:56PM +0800, Hawkins Jiawei wrote: > To be more specific, the simplified logic about original > tcindex_set_parms() is as below: > > static int > tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > u32 handle, struct tcindex_data *p, > struct tcindex_filter_result *r, struct nlattr **tb, > struct nlattr *est, u32 flags, struct netlink_ext_ack *extack) > { > ... > if (p->perfect) { > int i; > > if (tcindex_alloc_perfect_hash(net, cp) < 0) > goto errout; > cp->alloc_hash = cp->hash; > for (i = 0; i < min(cp->hash, p->hash); i++) > cp->perfect[i].res = p->perfect[i].res; > balloc = 1; > } > cp->h = p->h; > > ... > > if (cp->perfect) > r = cp->perfect + handle; We can reach here if p->perfect is non-NULL. > else > r = tcindex_lookup(cp, handle) ? : &new_filter_result; > > if (old_r && old_r != r) { > err = tcindex_filter_result_init(old_r, cp, net); > if (err < 0) { > kfree(f); > goto errout_alloc; > } > } > ... > } > > - cp's h field is directly copied from p's h field > > - if `old_r` is retrieved from struct tcindex_filter, in other word, > is retrieved from p's h field. Then the `r` should get the same value > from `tcindex_loopup(cp, handle)`. See above, 'r' can be 'cp->perfect + handle' which is newly allocated, hence different from 'old_r'. > > - so `old_r == r` is true, code will never uses tcindex_filter_result_init() > to clear the old_r in such case. Not always. > > So I think this patch still can fix this memory leak caused by > tcindex_filter_result_init(), But maybe I need to improve my > commit message. > I think your patch may introduce other memory leaks and 'old_r' may be left as obsoleted too. Thanks.
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