[PATCH bpf-next v2] selftests/bpf: Fix incorrect array size calculation

[Jiayuan Chen <jiayuan.chen@linux.dev>]

The loop in bench_sockmap_prog_destroy() has two issues:

1. Using 'sizeof(ctx.fds)' as the loop bound results in the number of
   bytes, not the number of file descriptors, causing the loop to iterate
   far more times than intended.

2. The condition 'ctx.fds[0] > 0' incorrectly checks only the first fd for
   all iterations, potentially leaving file descriptors unclosed. Change
   it to 'ctx.fds[i] > 0' to check each fd properly.

These fixes ensure correct cleanup of all file descriptors when the
benchmark exits.

Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/bpf/aLqfWuRR9R_KTe5e@stanley.mountain/
---
 tools/testing/selftests/bpf/benchs/bench_sockmap.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/benchs/bench_sockmap.c b/tools/testing/selftests/bpf/benchs/bench_sockmap.c
index 8ebf563a67a2..cfc072aa7fff 100644
--- a/tools/testing/selftests/bpf/benchs/bench_sockmap.c
+++ b/tools/testing/selftests/bpf/benchs/bench_sockmap.c
@@ -10,6 +10,7 @@
 #include <argp.h>
 #include "bench.h"
 #include "bench_sockmap_prog.skel.h"
+#include "bpf_util.h"
 
 #define FILE_SIZE (128 * 1024)
 #define DATA_REPEAT_SIZE 10
@@ -124,8 +125,8 @@ static void bench_sockmap_prog_destroy(void)
 {
 	int i;
 
-	for (i = 0; i < sizeof(ctx.fds); i++) {
-		if (ctx.fds[0] > 0)
+	for (i = 0; i < ARRAY_SIZE(ctx.fds); i++) {
+		if (ctx.fds[i] > 0)
 			close(ctx.fds[i]);
 	}
 
-- 
2.43.0