Commit a9384a4c authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

mld: respect RCU rules in ip6_mc_source() and ip6_mc_msfilter() 



Whenever RCU protected list replaces an object,
the pointer to the new object needs to be updated
_before_ the call to kfree_rcu() or call_rcu()

Also ip6_mc_msfilter() needs to update the pointer
before releasing the mc_lock mutex.

Note that linux-5.13 was supporting kfree_rcu(NULL, rcu),
so this fix does not need the conditional test I was
forced to use in the equivalent patch for IPv4.

Fixes: 882ba1f7 ("mld: convert ipv6_mc_socklist->sflist to RCU")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent dba5bdd5

net/ipv6/mcast.c

+4 −4
Original line number Diff line number Diff line
@@ -460,10 +460,10 @@ int ip6_mc_source(int add, int omode, struct sock *sk, 
				newpsl->sl_addr[i] = psl->sl_addr[i];

			atomic_sub(struct_size(psl, sl_addr, psl->sl_max),

				   &sk->sk_omem_alloc);

			kfree_rcu(psl, rcu);

		}

		rcu_assign_pointer(pmc->sflist, newpsl);

		kfree_rcu(psl, rcu);

		psl = newpsl;

		rcu_assign_pointer(pmc->sflist, psl);

	}

	rv = 1;	/* > 0 for insert logic below if sl_count is 0 */

	for (i = 0; i < psl->sl_count; i++) {
@@ -565,12 +565,12 @@ int ip6_mc_msfilter(struct sock *sk, struct group_filter *gsf, 
			       psl->sl_count, psl->sl_addr, 0);

		atomic_sub(struct_size(psl, sl_addr, psl->sl_max),

			   &sk->sk_omem_alloc);

		kfree_rcu(psl, rcu);

	} else {

		ip6_mc_del_src(idev, group, pmc->sfmode, 0, NULL, 0);

	}

	mutex_unlock(&idev->mc_lock);

	rcu_assign_pointer(pmc->sflist, newpsl);

	mutex_unlock(&idev->mc_lock);

	kfree_rcu(psl, rcu);

	pmc->sfmode = gsf->gf_fmode;

	err = 0;

done: