From: takeshi.iwanari <takeshi.iwanari@tier4.jp>
Date: Fri, 24 Jun 2022 13:17:39 +0000 (+0900)
Subject: Fix: Use negative value for error code of lttng_ust_ctl_duplicate_ust_object_data
X-Git-Tag: v2.12.6~7
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=2a2febe2ad7dae85101a679033b2d9b4b5926440;p=lttng-ust.git

Fix: Use negative value for error code of lttng_ust_ctl_duplicate_ust_object_data

[As is]
  - `lttng_ust_ctl_duplicate_ust_object_data` function is called by the following functions:
    - `event_notifier_error_accounting_register_app` (lttng-tools)
    - `duplicate_stream_object` (lttng-tools)
    - `duplicate_channel_object` (lttng-tools)
  - `lttng_ust_ctl_duplicate_ust_object_data` function returns positive value (= errno ＝ 24 = EMFILE) when system call `dup` returns error
  - However, `duplicate_stream_object` and `duplicate_channel_object` functions expect negative value as error code
  - As a result, these functions cannot handle error and segmentation fault occurs when using `stream->handle`

[Proposal]
  - Currently, `lttng_ust_ctl_duplicate_ust_object_data` function returns either positive or negative value when error happens
  - It looks convention is using negative value for error code (e.g. `-ENOMEM` )
  - So, I propose to change `errno` to `-errno`

Signed-off-by: takeshi.iwanari <takeshi.iwanari@tier4.jp>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Iccb01930413ecd5a8c58ad267e9c4eca53694dc7
---

diff --git a/liblttng-ust-ctl/ustctl.c b/liblttng-ust-ctl/ustctl.c
index 39860ebf..2dbac411 100644
--- a/liblttng-ust-ctl/ustctl.c
+++ b/liblttng-ust-ctl/ustctl.c
@@ -915,7 +915,7 @@ int ustctl_duplicate_ust_object_data(struct lttng_ust_object_data **dest,
 			obj->u.channel.wakeup_fd =
 				dup(src->u.channel.wakeup_fd);
 			if (obj->u.channel.wakeup_fd < 0) {
-				ret = errno;
+				ret = -errno;
 				goto chan_error_wakeup_fd;
 			}
 		} else {
@@ -951,7 +951,7 @@ int ustctl_duplicate_ust_object_data(struct lttng_ust_object_data **dest,
 			obj->u.stream.wakeup_fd =
 				dup(src->u.stream.wakeup_fd);
 			if (obj->u.stream.wakeup_fd < 0) {
-				ret = errno;
+				ret = -errno;
 				goto stream_error_wakeup_fd;
 			}
 		} else {
@@ -963,7 +963,7 @@ int ustctl_duplicate_ust_object_data(struct lttng_ust_object_data **dest,
 			obj->u.stream.shm_fd =
 				dup(src->u.stream.shm_fd);
 			if (obj->u.stream.shm_fd < 0) {
-				ret = errno;
+				ret = -errno;
 				goto stream_error_shm_fd;
 			}
 		} else {