diff --git a/musl_src.gni b/musl_src.gni
index 65d299b5300298fec638ab0894280e90d0446259..6ef104e9946142308d6a2b414e7a1c3200b293a7 100644
--- a/musl_src.gni
+++ b/musl_src.gni
@@ -2223,6 +2223,7 @@ musl_src_porting_file = [
   "src/misc/aarch64/syscall.s",
   "src/stdlib/strtod.c",
   "src/stdio/vfscanf.c",
+  "src/stdio/fileno.c",
 ]
 
 musl_inc_hook_files = [
diff --git a/porting/linux/user/src/stdio/fileno.c b/porting/linux/user/src/stdio/fileno.c
new file mode 100644
index 0000000000000000000000000000000000000000..1eea733cb6bb0c2a0eb748d648d955b6a821d976
--- /dev/null
+++ b/porting/linux/user/src/stdio/fileno.c
@@ -0,0 +1,20 @@
+#include "stdio_impl.h"
+#include <errno.h>
+
+int fileno_unlocked(FILE *f)
+{
+	int fd = f->fd;
+	if (fd < 0) {
+		errno = EBADF;
+		return -1;
+	}
+	return fd;
+}
+
+int fileno(FILE *f)
+{
+	FLOCK(f);
+	int fd = fileno_unlocked(f);
+	FUNLOCK(f);
+	return fd;
+}