Keep error pages out of the cache

3 files changed, 22 insertions, 3 deletions

diff --git a/source/cgit.c b/source/cgit.c
index ac8922b..12981c2 100644
--- a/source/cgit.c
+++ b/source/cgit.c
@@ -82,9 +82,8 @@ static void isolate_git_environment(void)
  */
 static NORETURN void die_routine(const char *msg, va_list params)
 {
-	// A page is rendered with stdout pointed at the cache file, so the
-	// message would otherwise be written there instead of to the visitor.
-	cache_abandon_fill();
+	// The error page abandons any cache fill in progress, so the message
+	// reaches the visitor rather than the cache file stdout points at.
 	cgit_vprint_error_page(400, "Bad request", msg, params);
 	exit(0);
 }
diff --git a/source/ui-shared.c b/source/ui-shared.c
index 066c25d..05fa30b 100644
--- a/source/ui-shared.c
+++ b/source/ui-shared.c
@@ -10,6 +10,7 @@
 
 #define USE_THE_REPOSITORY_VARIABLE
 
+#include "cache.h"
 #include "cgit.h"
 #include "html.h"
 #include "shared.h"
@@ -1293,6 +1294,11 @@ void cgit_print_error_page(int code, const char *msg, const char *fmt, ...)
 void cgit_vprint_error_page(int code, const char *msg, const char *fmt,
 			    va_list ap)
 {
+	// An error page describes a condition that may not outlast the slot
+	// holding it. A request naming a commit not yet pushed would cache its
+	// 404 under the never-expiring static ttl and keep serving it after
+	// the push, so the error is rendered straight to the visitor instead.
+	cache_abandon_fill();
 	ctx.page.status = code;
 	ctx.page.statusmsg = msg;
 	cgit_print_layout_start();
diff --git a/tests/t0020-validate-cache.sh b/tests/t0020-validate-cache.sh
index 0cf7433..feb6275 100755
--- a/tests/t0020-validate-cache.sh
+++ b/tests/t0020-validate-cache.sh
@@ -154,4 +154,18 @@ test_expect_success 'an ordinary key still fills a slot' '
 	test_line_count = 1 key.slots
 '
 
+# An error page reports a condition the repository may grow out of, and a
+# request pinned to an object id would cache it under the never-expiring
+# static ttl. Asking for a commit that does not exist yet must therefore
+# leave nothing behind, or the real page could never appear once it does.
+test_expect_success 'an error page leaves no slot behind' '
+	rm -rf cache3 && mkdir cache3 &&
+	CGIT_CONFIG="$PWD/bigkeyrc" \
+	QUERY_STRING="url=bigpage/commit/&id=0123456789abcdef0123456789abcdef01234567" \
+	cgit >error.out &&
+	grep "Bad commit reference" error.out &&
+	ls cache3 >error.slots &&
+	test_line_count = 0 error.slots
+'
+
 test_done