linux-kernel - [PATCH v2] selftests: uevent filtering: fix return on error in uevent

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Date:   Sun, 01 Oct 2023 10:37:44 +0200
From:   Javier Carrasco <javier.carrasco.cruz@...il.com>
To:     Shuah Khan <shuah@...nel.org>
Cc:     linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Javier Carrasco <javier.carrasco.cruz@...il.com>
Subject: [PATCH v2] selftests: uevent filtering: fix return on error in
 uevent_listener

The ret variable is used to check function return values and assigning
values to it on error has no effect as it is an unused value.

The current implementation uses an additional variable (fret) to return
the error value, which in this case is unnecessary and lead to the above
described misuse. There is no restriction in the current implementation
to always return -1 on error and the actual negative error value can be
returned safely without storing -1 in a specific variable.

Simplify the error checking by using a single variable which always
holds the returned value.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.com>
---
Changes in v2:
- Remove fret and use a single variable to check errors.
- Link to v1: https://lore.kernel.org/r/20230916-topic-self_uevent_filtering-v1-1-26ede507d454@gmail.com
---
 tools/testing/selftests/uevent/uevent_filtering.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/uevent/uevent_filtering.c b/tools/testing/selftests/uevent/uevent_filtering.c
index 5cebfb356345..dbe55f3a66f4 100644
--- a/tools/testing/selftests/uevent/uevent_filtering.c
+++ b/tools/testing/selftests/uevent/uevent_filtering.c
@@ -78,7 +78,7 @@ static int uevent_listener(unsigned long post_flags, bool expect_uevent,
 {
 	int sk_fd, ret;
 	socklen_t sk_addr_len;
-	int fret = -1, rcv_buf_sz = __UEVENT_BUFFER_SIZE;
+	int rcv_buf_sz = __UEVENT_BUFFER_SIZE;
 	uint64_t sync_add = 1;
 	struct sockaddr_nl sk_addr = { 0 }, rcv_addr = { 0 };
 	char buf[__UEVENT_BUFFER_SIZE] = { 0 };
@@ -121,6 +121,7 @@ static int uevent_listener(unsigned long post_flags, bool expect_uevent,
 
 	if ((size_t)sk_addr_len != sizeof(sk_addr)) {
 		fprintf(stderr, "Invalid socket address size\n");
+		ret = -1;
 		goto on_error;
 	}
 
@@ -147,11 +148,12 @@ static int uevent_listener(unsigned long post_flags, bool expect_uevent,
 	ret = write_nointr(sync_fd, &sync_add, sizeof(sync_add));
 	close(sync_fd);
 	if (ret != sizeof(sync_add)) {
+		ret = -1;
 		fprintf(stderr, "Failed to synchronize with parent process\n");
 		goto on_error;
 	}
 
-	fret = 0;
+	ret = 0;
 	for (;;) {
 		ssize_t r;
 
@@ -187,7 +189,7 @@ static int uevent_listener(unsigned long post_flags, bool expect_uevent,
 on_error:
 	close(sk_fd);
 
-	return fret;
+	return ret;
 }
 
 int trigger_uevent(unsigned int times)

---
base-commit: cefc06e4de1477dbdc3cb2a91d4b1873b7797a5c
change-id: 20230916-topic-self_uevent_filtering-17b53262bc46

Best regards,
-- 
Javier Carrasco <javier.carrasco.cruz@...il.com>