From: John Fastabend john.fastabend@gmail.com
commit 90db6d772f749e38171d04619a5e3cd8804a6d02 upstream.
The bucket->lock is not needed in the sock_hash_free and sock_map_free calls, in fact it is causing a splat due to being inside rcu block.
| BUG: sleeping function called from invalid context at net/core/sock.c:2935 | in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 62, name: kworker/0:1 | 3 locks held by kworker/0:1/62: | #0: ffff88813b019748 ((wq_completion)events){+.+.}, at: process_one_work+0x1d7/0x5e0 | #1: ffffc900000abe50 ((work_completion)(&map->work)){+.+.}, at: process_one_work+0x1d7/0x5e0 | #2: ffff8881381f6df8 (&stab->lock){+...}, at: sock_map_free+0x26/0x180 | CPU: 0 PID: 62 Comm: kworker/0:1 Not tainted 5.5.0-04008-g7b083332376e #454 | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014 | Workqueue: events bpf_map_free_deferred | Call Trace: | dump_stack+0x71/0xa0 | ___might_sleep.cold+0xa6/0xb6 | lock_sock_nested+0x28/0x90 | sock_map_free+0x5f/0x180 | bpf_map_free_deferred+0x58/0x80 | process_one_work+0x260/0x5e0 | worker_thread+0x4d/0x3e0 | kthread+0x108/0x140 | ? process_one_work+0x5e0/0x5e0 | ? kthread_park+0x90/0x90 | ret_from_fork+0x3a/0x50
The reason we have stab->lock and bucket->locks in sockmap code is to handle checking EEXIST in update/delete cases. We need to be careful during an update operation that we check for EEXIST and we need to ensure that the psock object is not in some partial state of removal/insertion while we do this. So both map_update_common and sock_map_delete need to guard from being run together potentially deleting an entry we are checking, etc. But by the time we get to the tear-down code in sock_{ma[|hash}_free we have already disconnected the map and we just did synchronize_rcu() in the line above so no updates/deletes should be in flight. Because of this we can drop the bucket locks from the map free'ing code, noting no update/deletes can be in-flight.
Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface") Reported-by: Jakub Sitnicki jakub@cloudflare.com Suggested-by: Jakub Sitnicki jakub@cloudflare.com Signed-off-by: John Fastabend john.fastabend@gmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/158385850787.30597.8346421465837046618.stgit@joh... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/core/sock_map.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
--- a/net/core/sock_map.c +++ b/net/core/sock_map.c @@ -233,8 +233,11 @@ static void sock_map_free(struct bpf_map struct bpf_stab *stab = container_of(map, struct bpf_stab, map); int i;
+ /* After the sync no updates or deletes will be in-flight so it + * is safe to walk map and remove entries without risking a race + * in EEXIST update case. + */ synchronize_rcu(); - raw_spin_lock_bh(&stab->lock); for (i = 0; i < stab->map.max_entries; i++) { struct sock **psk = &stab->sks[i]; struct sock *sk; @@ -248,7 +251,6 @@ static void sock_map_free(struct bpf_map release_sock(sk); } } - raw_spin_unlock_bh(&stab->lock);
/* wait for psock readers accessing its map link */ synchronize_rcu(); @@ -863,10 +865,13 @@ static void sock_hash_free(struct bpf_ma struct hlist_node *node; int i;
+ /* After the sync no updates or deletes will be in-flight so it + * is safe to walk map and remove entries without risking a race + * in EEXIST update case. + */ synchronize_rcu(); for (i = 0; i < htab->buckets_num; i++) { bucket = sock_hash_select_bucket(htab, i); - raw_spin_lock_bh(&bucket->lock); hlist_for_each_entry_safe(elem, node, &bucket->head, node) { hlist_del_rcu(&elem->node); lock_sock(elem->sk); @@ -875,7 +880,6 @@ static void sock_hash_free(struct bpf_ma rcu_read_unlock(); release_sock(elem->sk); } - raw_spin_unlock_bh(&bucket->lock); }
/* wait for psock readers accessing its map link */