When xsend() returns -1 (error), the check 'n < sizeof(buf)' incorrectly
treats it as success due to unsigned promotion. Explicitly check for -1
first.

Fixes: a4b7193d8efd ("selftests/bpf: Add sockmap test for redirecting partial skb data")
Signed-off-by: wangfushuai <wangfushuai@baidu.com>
---
 tools/testing/selftests/bpf/prog_tests/sockmap_listen.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c
index 1d98eee7a2c3..f1bdccc7e4e7 100644
--- a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c
+++ b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c
@@ -924,6 +924,8 @@ static void redir_partial(int family, int sotype, int sock_map, int parser_map)
 		goto close;
 
 	n = xsend(c1, buf, sizeof(buf), 0);
+	if (n == -1)
+		goto close;
 	if (n < sizeof(buf))
 		FAIL("incomplete write");
 
-- 
2.36.1

On Sun, Jun 8, 2025 at 7:38 AM wangfushuai <wangfushuai@baidu.com> wrote:
>
> When xsend() returns -1 (error), the check 'n < sizeof(buf)' incorrectly
> treats it as success due to unsigned promotion. Explicitly check for -1
> first.
>
> Fixes: a4b7193d8efd ("selftests/bpf: Add sockmap test for redirecting partial skb data")
> Signed-off-by: wangfushuai <wangfushuai@baidu.com>

Looks good, but please spell out your name as First Last
in both From and Signed-off

Also use [PATCH bpf-next] in subject

pw-bot: cr

> ---
>  tools/testing/selftests/bpf/prog_tests/sockmap_listen.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c
> index 1d98eee7a2c3..f1bdccc7e4e7 100644
> --- a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c
> +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c
> @@ -924,6 +924,8 @@ static void redir_partial(int family, int sotype, int sock_map, int parser_map)
>                 goto close;
>
>         n = xsend(c1, buf, sizeof(buf), 0);
> +       if (n == -1)
> +               goto close;
>         if (n < sizeof(buf))
>                 FAIL("incomplete write");
>
> --
> 2.36.1
>

>> When xsend() returns -1 (error), the check 'n < sizeof(buf)' incorrectly
>> treats it as success due to unsigned promotion. Explicitly check for -1
>> first.
>>
>> Fixes: a4b7193d8efd ("selftests/bpf: Add sockmap test for redirecting partial skb data")
>> Signed-off-by: wangfushuai <wangfushuai@baidu.com>
> 
> Looks good, but please spell out your name as First Last
> in both From and Signed-off
> 
> Also use [PATCH bpf-next] in subject
> 
> pw-bot: cr

Will fix and send v2 shortly. Thanks for the review!

--
Regards,
Wang
 
>> ---
>>  tools/testing/selftests/bpf/prog_tests/sockmap_listen.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c
>> index 1d98eee7a2c3..f1bdccc7e4e7 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c
>> @@ -924,6 +924,8 @@ static void redir_partial(int family, int sotype, int sock_map, int parser_map)
>>                 goto close;
>>
>>         n = xsend(c1, buf, sizeof(buf), 0);
>> +       if (n == -1)
>> +               goto close;
>>         if (n < sizeof(buf))
>>                 FAIL("incomplete write");
>>
>> --
>> 2.36.1