Commit 5720a328 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Paolo Abeni
Browse files

ipv6: Preallocate rt->fib6_nh->rt6i_pcpu in ip6_route_info_create(). 



ip6_route_info_create_nh() will be called under RCU.

Then, fib6_nh_init() is also under RCU, but per-cpu memory allocation
is very likely to fail with GFP_ATOMIC while bulk-adding IPv6 routes
and we would see a bunch of this message in dmesg.

  percpu: allocation failed, size=8 align=8 atomic=1, atomic alloc failed, no space left
  percpu: allocation failed, size=8 align=8 atomic=1, atomic alloc failed, no space left

Let's preallocate rt->fib6_nh->rt6i_pcpu in ip6_route_info_create().

If something fails before the original memory allocation in
fib6_nh_init(), ip6_route_info_create_nh() calls fib6_info_release(),
which releases the preallocated per-cpu memory.

Note that rt->fib6_nh->rt6i_pcpu is not preallocated when called via
ipv6_stub, so we still need alloc_percpu_gfp() in fib6_nh_init().

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250418000443.43734-8-kuniyu@amazon.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent c4837b98

net/ipv6/route.c

+22 −3
Original line number Diff line number Diff line
@@ -3665,11 +3665,13 @@ int fib6_nh_init(struct net *net, struct fib6_nh *fib6_nh, 
		goto out;



pcpu_alloc:

	if (!fib6_nh->rt6i_pcpu) {

		fib6_nh->rt6i_pcpu = alloc_percpu_gfp(struct rt6_info *, gfp_flags);

		if (!fib6_nh->rt6i_pcpu) {

			err = -ENOMEM;

			goto out;

		}

	}



	fib6_nh->fib_nh_dev = dev;

	fib6_nh->fib_nh_oif = dev->ifindex;
@@ -3728,6 +3730,15 @@ void fib6_nh_release_dsts(struct fib6_nh *fib6_nh) 
	}

}



static int fib6_nh_prealloc_percpu(struct fib6_nh *fib6_nh, gfp_t gfp_flags)

{

	fib6_nh->rt6i_pcpu = alloc_percpu_gfp(struct rt6_info *, gfp_flags);

	if (!fib6_nh->rt6i_pcpu)

		return -ENOMEM;



	return 0;

}



static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,

					       gfp_t gfp_flags,

					       struct netlink_ext_ack *extack)
@@ -3765,6 +3776,12 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg, 
		goto free;

	}



	if (!cfg->fc_nh_id) {

		err = fib6_nh_prealloc_percpu(&rt->fib6_nh[0], gfp_flags);

		if (err)

			goto free_metrics;

	}



	if (cfg->fc_flags & RTF_ADDRCONF)

		rt->dst_nocount = true;
@@ -3789,6 +3806,8 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg, 
	rt->fib6_src.plen = cfg->fc_src_len;

#endif

	return rt;

free_metrics:

	ip_fib_metrics_put(rt->fib6_metrics);

free:

	kfree(rt);

err: