[PATCH 5.12 158/178] cfg80211: make certificate generation more robust

[Greg Kroah-Hartman]

From: Johannes Berg <johannes.berg@xxxxxxxxx>

commit b5642479b0f7168fe16d156913533fe65ab4f8d5 upstream.

If all net/wireless/certs/*.hex files are deleted, the build
will hang at this point since the 'cat' command will have no
arguments. Do "echo | cat - ..." so that even if the "..."
part is empty, the whole thing won't hang.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Luca Coelho <luciano.coelho@xxxxxxxxx>
Link: https://lore.kernel.org/r/iwlwifi.20210618133832.c989056c3664.Ic3b77531d00b30b26dcd69c64e55ae2f60c3f31e@changeid
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/wireless/Makefile |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/wireless/Makefile
+++ b/net/wireless/Makefile
@@ -28,7 +28,7 @@ $(obj)/shipped-certs.c: $(wildcard $(src
 	@$(kecho) "  GEN     $@"
 	@(echo '#include "reg.h"'; \
 	  echo 'const u8 shipped_regdb_certs[] = {'; \
-	  cat $^ ; \
+	  echo | cat - $^ ; \
 	  echo '};'; \
 	  echo 'unsigned int shipped_regdb_certs_len = sizeof(shipped_regdb_certs);'; \
 	 ) > $@