[PATCH v7] [GSOC] ref-filter: fix read invalid union member bug

From: ZheNing Hu via GitGitGadget <gitgitgadget@gmail.com>
Date: May 13, 2021, 15:13 UTC
Message-ID: <pull.949.v7.git.1620918814489.gitgitgadget@gmail.com>
In-Reply-To: <pull.949.v6.git.1620821572126.gitgitgadget@gmail.com>

From: ZheNing Hu <adlternative@gmail.com>

used_atom.u is an union, and it has different members depending on what atom the auxiliary data the union part of the "struct used_atom" wants to record. At most only one of the members can be valid at any one time. Since the code checks u.remote_ref without even making sure if the atom is "push" or "push:" (which are only two cases that u.remote_ref.push becomes valid), but u.remote_ref shares the same storage for other members of the union, the check was reading from an invalid member, which was the bug.

Modify the condition here to check whether the atom name equals to "push" or starts with "push:", to avoid reading the value of invalid member of the union.

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: ZheNing Hu <adlternative@gmail.com>
---
    [GSOC] ref-filter: fix read invalid union member bug
    
    Change from last version: Modify the test content, reduce additional
    'mkdir' operation and remove temp-dir "test" when finished.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-949%2Fadlternative%2Fref-filter-enum-bug-fix-v7
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-949/adlternative/ref-filter-enum-bug-fix-v7
Pull-Request: https://github.com/gitgitgadget/git/pull/949

Range-diff vs v6:

 1:  518cc41a78a4 ! 1:  50bef8439a85 [GSOC] ref-filter: fix read invalid union member bug
     @@ t/t6302-for-each-ref-filter.sh: test_expect_success '%(color) must fail' '
       '
       
      +test_expect_success '%(color:#aa22ac) must succeed' '
     -+	mkdir test &&
     ++	test_when_finished rm -fr test &&
      +	git init test &&
      +	(
      +		cd test &&

 ref-filter.c                   |  2 +-
 t/t6302-for-each-ref-filter.sh | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/ref-filter.c b/ref-filter.c
index a0adb4551d87..213d3773ada3 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -1730,7 +1730,7 @@ static int populate_value(struct ref_array_item *ref, struct strbuf *err)
 			else
 				v->s = xstrdup("");
 			continue;
-		} else if (atom->u.remote_ref.push) {
+		} else if (!strcmp(atom->name, "push") || starts_with(atom->name, "push:")) {
 			const char *branch_name;
 			v->s = xstrdup("");
 			if (!skip_prefix(ref->refname, "refs/heads/",
diff --git a/t/t6302-for-each-ref-filter.sh b/t/t6302-for-each-ref-filter.sh
index 9866b1b57368..5070d0cf1e80 100755
--- a/t/t6302-for-each-ref-filter.sh
+++ b/t/t6302-for-each-ref-filter.sh
@@ -117,6 +117,25 @@ test_expect_success '%(color) must fail' '
 	test_must_fail git for-each-ref --format="%(color)%(refname)"
 '
 
+test_expect_success '%(color:#aa22ac) must succeed' '
+	test_when_finished rm -fr test &&
+	git init test &&
+	(
+		cd test &&
+		test_commit initial &&
+		git branch -M main &&
+		cat >expect <<-\EOF &&
+		refs/heads/main
+		refs/tags/initial
+		EOF
+		git remote add origin nowhere &&
+		git config branch.main.remote origin &&
+		git config branch.main.merge refs/heads/main &&
+		git for-each-ref --format="%(color:#aa22ac)%(refname)" >actual &&
+		test_cmp expect actual
+	)
+'
+
 test_expect_success 'left alignment is default' '
 	cat >expect <<-\EOF &&
 	refname is refs/heads/main    |refs/heads/main

base-commit: 311531c9de557d25ac087c1637818bd2aad6eb3a

-- 
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