[PATCH 5.10 093/104] net: fix iteration for sctp transport seq_files

Greg Kroah-Hartman
2021-02-15T15:43:28Z

From: NeilBrown <neilb@suse.de>

commit af8085f3a4712c57d0dd415ad543bac85780375c upstream.

The sctp transport seq_file iterators take a reference to the transport
in the ->start and ->next functions and releases the reference in the
->show function. The preferred handling for such resources is to
release them in the subsequent ->next or ->stop function call.

Since Commit 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration
code and interface") there is no guarantee that ->show will be called
after ->next, so this function can now leak references.

So move the sctp_transport_put() call to ->next and ->stop.

Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and interface")
Reported-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sctp/proc.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

--- a/net/sctp/proc.c
+++ b/net/sctp/proc.c
@@ -215,6 +215,12 @@ static void sctp_transport_seq_stop(stru
{
struct sctp_ht_iter *iter = seq->private;

+ if (v && v != SEQ_START_TOKEN) {
+ struct sctp_transport *transport = v;
+
+ sctp_transport_put(transport);
+ }
+
sctp_transport_walk_stop(&iter->hti);
}

@@ -222,6 +228,12 @@ static void *sctp_transport_seq_next(str
{
struct sctp_ht_iter *iter = seq->private;

+ if (v && v != SEQ_START_TOKEN) {
+ struct sctp_transport *transport = v;
+
+ sctp_transport_put(transport);
+ }
+
++*pos;

return sctp_transport_get_next(seq_file_net(seq), &iter->hti);
@@ -277,8 +289,6 @@ static int sctp_assocs_seq_show(struct s
sk->sk_rcvbuf);
seq_printf(seq, "\n");

- sctp_transport_put(transport);
-
return 0;
}

@@ -354,8 +364,6 @@ static int sctp_remaddr_seq_show(struct
seq_printf(seq, "\n");
}

- sctp_transport_put(transport);
-
return 0;
}