[RFC PATCH bpf-next 03/14] bpf: Hold socket lock in socket map iterator
From: Jordan Rife <hidden>
Date: 2025-09-09 17:00:27
Also in:
bpf
Subsystem:
bpf [l7 framework] (sockmap), networking [general], networking [sockets], the rest · Maintainers:
John Fastabend, Jakub Sitnicki, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kuniyuki Iwashima, Willem de Bruijn, Linus Torvalds
Similar to socket hash iterators, decouple reading from processing to enable bpf_iter_run_prog to run while holding the socket lock and take a reference to the current socket to ensure that it isn't freed outside of the RCU read-side critical section. Signed-off-by: Jordan Rife <redacted> --- net/core/sock_map.c | 33 ++++++++++++++++++++++++--------- 1 file changed, 24 insertions(+), 9 deletions(-)
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 9d972069665b..f33bfce96b9e 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c@@ -723,30 +723,39 @@ static void *sock_map_seq_lookup_elem(struct sock_map_seq_info *info) if (unlikely(info->index >= info->map->max_entries)) return NULL; + rcu_read_lock(); info->sk = __sock_map_lookup_elem(info->map, info->index); + if (info->sk) + sock_hold(info->sk); + rcu_read_unlock(); /* can't return sk directly, since that might be NULL */ return info; } +static void sock_map_seq_put_elem(struct sock_map_seq_info *info) +{ + if (info->sk) { + sock_put(info->sk); + info->sk = NULL; + } +} + static void *sock_map_seq_start(struct seq_file *seq, loff_t *pos) - __acquires(rcu) { struct sock_map_seq_info *info = seq->private; if (*pos == 0) ++*pos; - /* pairs with sock_map_seq_stop */ - rcu_read_lock(); return sock_map_seq_lookup_elem(info); } static void *sock_map_seq_next(struct seq_file *seq, void *v, loff_t *pos) - __must_hold(rcu) { struct sock_map_seq_info *info = seq->private; + sock_map_seq_put_elem(info); ++*pos; ++info->index;
@@ -754,12 +763,12 @@ static void *sock_map_seq_next(struct seq_file *seq, void *v, loff_t *pos) } static int sock_map_seq_show(struct seq_file *seq, void *v) - __must_hold(rcu) { struct sock_map_seq_info *info = seq->private; struct bpf_iter__sockmap ctx = {}; struct bpf_iter_meta meta; struct bpf_prog *prog; + int ret; meta.seq = seq; prog = bpf_iter_get_info(&meta, !v);
@@ -773,17 +782,23 @@ static int sock_map_seq_show(struct seq_file *seq, void *v) ctx.sk = info->sk; } - return bpf_iter_run_prog(prog, &ctx); + if (ctx.sk) + lock_sock(ctx.sk); + ret = bpf_iter_run_prog(prog, &ctx); + if (ctx.sk) + release_sock(ctx.sk); + + return ret; } static void sock_map_seq_stop(struct seq_file *seq, void *v) - __releases(rcu) { + struct sock_map_seq_info *info = seq->private; + if (!v) (void)sock_map_seq_show(seq, NULL); - /* pairs with sock_map_seq_start */ - rcu_read_unlock(); + sock_map_seq_put_elem(info); } static const struct seq_operations sock_map_seq_ops = {
--
2.43.0