[PATCH v4] [GSOC] ref-filter: fix read invalid union member bug

From: ZheNing Hu via GitGitGadget <gitgitgadget@gmail.com>
Date: May 10, 2021, 15:01 UTC
Message-ID: <pull.949.v4.git.1620658904283.gitgitgadget@gmail.com>
In-Reply-To: <pull.949.v3.git.1620487572222.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:
    Prove that the bug may appear when using %(color) atom. And add
    corresponding test for it.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-949%2Fadlternative%2Fref-filter-enum-bug-fix-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-949/adlternative/ref-filter-enum-bug-fix-v4
Pull-Request: https://github.com/gitgitgadget/git/pull/949

Range-diff vs v3:

 1:  21cf7a44e168 ! 1:  8c6c0368a590 [GSOC] ref-filter: fix read invalid union member bug
     @@ ref-filter.c: static int populate_value(struct ref_array_item *ref, struct strbu
       			const char *branch_name;
       			v->s = xstrdup("");
       			if (!skip_prefix(ref->refname, "refs/heads/",
     +
     + ## t/t6302-for-each-ref-filter.sh ##
     +@@ t/t6302-for-each-ref-filter.sh: test_expect_success '%(color) must fail' '
     + 	test_must_fail git for-each-ref --format="%(color)%(refname)"
     + '
     + 
     ++test_expect_success '%(color:#aa22ac) must success' '
     ++	cat >expect <<-\EOF &&
     ++	refs/heads/main
     ++	refs/heads/side
     ++	refs/odd/spot
     ++	refs/tags/annotated-tag
     ++	refs/tags/doubly-annotated-tag
     ++	refs/tags/doubly-signed-tag
     ++	refs/tags/four
     ++	refs/tags/one
     ++	refs/tags/signed-tag
     ++	refs/tags/three
     ++	refs/tags/two
     ++	EOF
     ++	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

 ref-filter.c                   |  2 +-
 t/t6302-for-each-ref-filter.sh | 18 ++++++++++++++++++
 2 files changed, 19 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..38a7d83830aa 100755
--- a/t/t6302-for-each-ref-filter.sh
+++ b/t/t6302-for-each-ref-filter.sh
@@ -117,6 +117,24 @@ test_expect_success '%(color) must fail' '
 	test_must_fail git for-each-ref --format="%(color)%(refname)"
 '
 
+test_expect_success '%(color:#aa22ac) must success' '
+	cat >expect <<-\EOF &&
+	refs/heads/main
+	refs/heads/side
+	refs/odd/spot
+	refs/tags/annotated-tag
+	refs/tags/doubly-annotated-tag
+	refs/tags/doubly-signed-tag
+	refs/tags/four
+	refs/tags/one
+	refs/tags/signed-tag
+	refs/tags/three
+	refs/tags/two
+	EOF
+	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

-- 
gitgitgadget