The Close() macro uses the passed in expression three times, which
leads to repeated execution in case it has side effects. That is,
Close(i--) would decrement i three times.

ASAN caught a stack-buffer-undeflow error at a point where this was
overlooked. Fix it.

Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 tools/testing/selftests/bpf/prog_tests/fd_array.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/fd_array.c b/tools/testing/selftests/bpf/prog_tests/fd_array.c
index c534b4d5f9da..3078d8264deb 100644
--- a/tools/testing/selftests/bpf/prog_tests/fd_array.c
+++ b/tools/testing/selftests/bpf/prog_tests/fd_array.c
@@ -412,8 +412,8 @@ static void check_fd_array_cnt__fd_array_too_big(void)
 	ASSERT_EQ(prog_fd, -E2BIG, "prog should have been rejected with -E2BIG");
 
 cleanup_fds:
-	while (i > 0)
-		Close(extra_fds[--i]);
+	while (i-- > 0)
+		Close(extra_fds[i]);
 }
 
 void test_fd_array_cnt(void)
-- 
2.53.0

On Wed, 2026-02-11 at 17:13 -0800, Ihor Solodrai wrote:
> The Close() macro uses the passed in expression three times, which
> leads to repeated execution in case it has side effects. That is,
> Close(i--) would decrement i three times.
> 
> ASAN caught a stack-buffer-undeflow error at a point where this was
> overlooked. Fix it.
> 
> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
> ---

Acked-by: Eduard Zingerman <eddyz87@gmail.com>

(However, in bpf headers the common pattern is to define a variable
 in the macro body, something like `int ___fd = (FD);).

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