Messages in this thread | | | Date | Tue, 15 Nov 2022 09:02:37 -0800 | From | Jakub Kicinski <> | Subject | Re: [PATCH v2] net: sched: fix memory leak in tcindex_set_parms |
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On Mon, 14 Nov 2022 01:05:08 +0800 Hawkins Jiawei wrote: > diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c > index 1c9eeb98d826..d2fac9559d3e 100644 > --- a/net/sched/cls_tcindex.c > +++ b/net/sched/cls_tcindex.c > @@ -338,6 +338,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > struct tcf_result cr = {}; > int err, balloc = 0; > struct tcf_exts e; > + struct tcf_exts old_e = {};
This is not a valid way of initializing a structure. tcf_exts_init() is supposed to be called. If we add a list member to that structure this code will break, again.
> err = tcf_exts_init(&e, net, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE); > if (err < 0) > @@ -479,6 +480,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > } > > if (old_r && old_r != r) { > + old_e = old_r->exts; > err = tcindex_filter_result_init(old_r, cp, net); > if (err < 0) { > kfree(f); > @@ -510,6 +512,12 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, > tcf_exts_destroy(&new_filter_result.exts); > } > > + /* Note: old_e should be destroyed after the RCU grace period, > + * to avoid possible use-after-free by concurrent readers. > + */ > + synchronize_rcu(); > + tcf_exts_destroy(&old_e);
I don't think this dance is required, @cp is a copy of the original data, and the original (@p) is destroyed in a safe manner below.
> if (oldp) > tcf_queue_work(&oldp->rwork, tcindex_partial_destroy_work); > return 0;
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