pkg/vcs: Unset various git environment variables when invoking git

If you try to run git-using tests while the GIT_DIR environment variable
(and GIT_WORK_TREE, etc) happens to be set, the tests are going to do fun
and exciting things on a repository that isn't the test repository it tries
to set up.

As it turns out, if you try to run "make test" using git rebase -x, you'll
end up with GIT_DIR set to the syzkaller tree. Hilarity ensues.

Unset GIT_DIR, GIT_WORK_TREE and a few other environment variables when
invoking git - that way it'll default to looking at the working directory
that we have given it, which is what we expect.

Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>

3 files changed, 32 insertions, 2 deletions

diff --git a/pkg/vcs/git.go b/pkg/vcs/git.go
index a42f12edc..27064de7b 100644
--- a/pkg/vcs/git.go
+++ b/pkg/vcs/git.go
@@ -33,6 +33,26 @@ func newGit(dir string, ignoreCC map[string]bool) *git {
 	}
 }
 
+func filterEnv() []string {
+	// We have to filter various git environment variables - if
+	// these variables are set (e.g. if a test is being run as
+	// part of a rebase) we're going to be acting on some other
+	// repository (e.g the syzkaller tree itself) rather than the
+	// intended repo.
+	env := os.Environ()
+	for i := 0; i < len(env); i++ {
+		if strings.HasPrefix(env[i], "GIT_DIR") ||
+			strings.HasPrefix(env[i], "GIT_WORK_TREE") ||
+			strings.HasPrefix(env[i], "GIT_INDEX_FILE") ||
+			strings.HasPrefix(env[i], "GIT_OBJECT_DIRECTORY") {
+			env = append(env[:i], env[i+1:]...)
+			i--
+		}
+	}
+
+	return env
+}
+
 func (git *git) Poll(repo, branch string) (*Commit, error) {
 	git.reset()
 	origin, err := git.git("remote", "get-url", "origin")
@@ -315,6 +335,7 @@ func (git *git) fetchCommits(since, base, user, domain string, greps []string, f
 	args = append(args, base)
 	cmd := exec.Command("git", args...)
 	cmd.Dir = git.dir
+	cmd.Env = filterEnv()
 	if err := osutil.Sandbox(cmd, true, false); err != nil {
 		return nil, err
 	}
@@ -359,7 +380,7 @@ func (git *git) fetchCommits(since, base, user, domain string, greps []string, f
 }
 
 func (git *git) git(args ...string) ([]byte, error) {
-	return runSandboxed(git.dir, "git", args...)
+	return runSandboxedEnv(git.dir, "git", filterEnv(), args...)
 }
 
 func splitEmail(email string) (user, domain string, err error) {
diff --git a/pkg/vcs/git_test_util.go b/pkg/vcs/git_test_util.go
index 86713bac0..2f050a2b2 100644
--- a/pkg/vcs/git_test_util.go
+++ b/pkg/vcs/git_test_util.go
@@ -25,7 +25,11 @@ type TestRepo struct {
 }
 
 func (repo *TestRepo) Git(args ...string) {
-	if _, err := osutil.RunCmd(time.Minute, repo.Dir, "git", args...); err != nil {
+	cmd := osutil.Command("git", args...)
+	cmd.Dir = repo.Dir
+	cmd.Env = filterEnv()
+
+	if _, err := osutil.Run(time.Minute, cmd); err != nil {
 		repo.t.Fatal(err)
 	}
 }
diff --git a/pkg/vcs/vcs.go b/pkg/vcs/vcs.go
index 23c906087..647a00f42 100644
--- a/pkg/vcs/vcs.go
+++ b/pkg/vcs/vcs.go
@@ -167,8 +167,13 @@ func CheckCommitHash(hash string) bool {
 }
 
 func runSandboxed(dir, command string, args ...string) ([]byte, error) {
+	return runSandboxedEnv(dir, command, nil, args...)
+}
+
+func runSandboxedEnv(dir, command string, env []string, args ...string) ([]byte, error) {
 	cmd := osutil.Command(command, args...)
 	cmd.Dir = dir
+	cmd.Env = env
 	if err := osutil.Sandbox(cmd, true, false); err != nil {
 		return nil, err
 	}