neels has uploaded this change for review.

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clarify API doc for osmo_pfcp_endpoint_tx()

I recently discovered some use-after-free in osmo-upf by wrong API usage
of osmo_pfcp_endpoint_tx(). Highlight this pitfall in API doc.

Change-Id: I637e7bb5d1296b5ad8db8ab0b8151fdbb9e7be03
---
M src/libosmo-pfcp/pfcp_endpoint.c
1 file changed, 6 insertions(+), 1 deletion(-)

git pull ssh://gerrit.osmocom.org:29418/libosmo-pfcp refs/changes/60/31260/1

diff --git a/src/libosmo-pfcp/pfcp_endpoint.c b/src/libosmo-pfcp/pfcp_endpoint.c
index 83a689f..7e08d8e 100644
--- a/src/libosmo-pfcp/pfcp_endpoint.c
+++ b/src/libosmo-pfcp/pfcp_endpoint.c
@@ -326,7 +326,12 @@
  * Store the message in the local message queue for possible retransmissions.
  * On success, return zero, and pass ownership of m to ep. ep deallocates m when all retransmissions are done / a reply
  * has been received.
- * On error, return nonzero, and immediately deallocate m. */
+ * On error, return nonzero, and immediately deallocate m.
+ *
+ * WARNING: Do not access the osmo_pfcp_msg m after calling this function! In most cases, m will still remain allocated,
+ * and accessing it will work, but especially when an error occurs, m will be deallocated immediately. Hence, you will
+ * see no problem during normal successful operation, but your program will crash with use-after-free on any error!
+ */
 int osmo_pfcp_endpoint_tx(struct osmo_pfcp_endpoint *ep, struct osmo_pfcp_msg *m)
 {
 	struct osmo_pfcp_ie_node_id *node_id;

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