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git: protect against unbalanced calls to {save,restore}_env()

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We made sure that save_env_before_alias() does not skip saving the
environment when asked to (which led to use-after-free of orig_cwd
in restore_env() in the buggy version) with the previous step.

Protect against future breakage where somebody adds new callers of
these functions in an unbalanced fashion.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Junio C Hamano
2016-01-26 22:50:27 -08:00
parent 9d1d2b7fad
commit 2e1175d43d
1 changed files with 7 additions and 0 deletions
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7
git.c
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@ -26,11 +26,15 @@ static const char *env_names[] = {
}; };
static char *orig_env[4]; static char *orig_env[4];
static int saved_env_before_alias; static int saved_env_before_alias;
static int save_restore_env_balance;
static void save_env_before_alias(void) static void save_env_before_alias(void)
{ {
int i; int i;
saved_env_before_alias = 1; saved_env_before_alias = 1;
assert(save_restore_env_balance == 0);
save_restore_env_balance = 1;
orig_cwd = xgetcwd(); orig_cwd = xgetcwd();
for (i = 0; i < ARRAY_SIZE(env_names); i++) { for (i = 0; i < ARRAY_SIZE(env_names); i++) {
orig_env[i] = getenv(env_names[i]); orig_env[i] = getenv(env_names[i]);
@ -42,6 +46,9 @@ static void save_env_before_alias(void)
static void restore_env(int external_alias) static void restore_env(int external_alias)
{ {
int i; int i;
assert(save_restore_env_balance == 1);
save_restore_env_balance = 0;
if (!external_alias && orig_cwd && chdir(orig_cwd)) if (!external_alias && orig_cwd && chdir(orig_cwd))
die_errno("could not move to %s", orig_cwd); die_errno("could not move to %s", orig_cwd);
free(orig_cwd); free(orig_cwd);