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

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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: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250418000443.43734-8-kuniyu@amazon.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kuniyuki Iwashima 2025-04-17 17:03:48 -07:00 committed by Paolo Abeni
parent c4837b9853
commit 5720a328c3
1 changed files with 22 additions and 3 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

25
net/ipv6/route.c
View file

@ -3665,10 +3665,12 @@ int fib6_nh_init(struct net *net, struct fib6_nh *fib6_nh,
goto out;
pcpu_alloc:
fib6_nh->rt6i_pcpu = alloc_percpu_gfp(struct rt6_info *, gfp_flags);
if (!fib6_nh->rt6i_pcpu) {
err = -ENOMEM;
goto out;
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;
@ -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: