diff options
| author |   Kuniyuki Iwashima <kuniyu@google.com> | 2026-09-18 08:22:05 +0000 |
|---|---|---|
| committer |   Jakub Kicinski <kuba@kernel.org> | 2026-09-21 16:20:00 -0700 |
| commit | 0346ec2f080b40d95ed05b853bb9226289e75212 (patch) | |
| tree | e901d2c9ae13e90d1a8bc72bc345e65d93c09289 | |
| parent | octeontx2-af: Fix memory scaling limitation in SR-IOV mode (diff) | |
ipv6: Prevent rt6_insert_exception() for dying fib6_info.
Before the cited commit, fib6_nh_flush_exceptions() always set
from->exception_bucket_flushed = 1 under rt6_exception_lock to
prevent rt6_insert_exception() from inserting a new exception
for a dying fib6_info.
The flag was replaced with the FIB6_EXCEPTION_BUCKET_FLUSHED
bit stored in nh->rt6i_exception_bucket.
The problem is that now the bit is only set when the bucket
is not NULL and fib6_nh_flush_exceptions() is called from
fib6_nh_release() after fib6_ref has already reached zero.
If rt6_insert_exception() is called while the target fib6_info
is being removed via fib6_purge_rt(), a new exception could be
created successfully because rt6_flush_exceptions() no longer
sets the bit.
This creates a reference cycle between the fib6_info and the
exception route, leaking the fib6_info, its nexthop device,
and all per-CPU routes in fib6_nh->rt6i_pcpu, which stalls netdev
unregistration.
[ 34.680602] unregister_netdevice: waiting for gre6 to become free. Usage count = 68
[ 44.920675] unregister_netdevice: waiting for gre6 to become free. Usage count = 68
[ 55.176582] unregister_netdevice: waiting for gre6 to become free. Usage count = 68
Let's call fib6_drop_pcpu_from() before rt6_flush_exceptions(),
to set fib6_destroying before rt6_exception_lock, and check
f6i->fib6_destroying in rt6_insert_exception().
Note that FIB6_EXCEPTION_BUCKET_FLUSHED logic is dead and
we can clean it up in net-next.
Fixes: cc5c073a693f ("ipv6: Move exception bucket to fib6_nh")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260918082209.2853582-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/ipv6/ip6_fib.c | 2 | ||||
| -rw-r--r-- | net/ipv6/route.c | 5 |
2 files changed, 6 insertions, 1 deletions
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index 9ea75703b38d..9ff761962b45 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -1043,8 +1043,8 @@ static void fib6_purge_rt(struct fib6_info *rt, struct fib6_node *fn, struct fib6_table *table = rt->fib6_table; /* Flush all cached dst in exception table */ - rt6_flush_exceptions(rt); fib6_drop_pcpu_from(rt); + rt6_flush_exceptions(rt); if (rt->nh) { spin_lock(&rt->nh->lock); diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 08bd68f1b5bb..884d9ab0d50d 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1729,6 +1729,11 @@ static int rt6_insert_exception(struct rt6_info *nrt, spin_lock_bh(&rt6_exception_lock); + if (f6i->fib6_destroying) { + err = -ENOENT; + goto out; + } + bucket = rcu_dereference_protected(nh->rt6i_exception_bucket, lockdep_is_held(&rt6_exception_lock)); if (!bucket) { |