pager: fix crash when pager program doesn't exist

When prepare_cmd() fails for, e.g., pager process setup,
child_process_clear() frees the memory in pager_process.args, but .argv
was pointed to pager_process.args.v earlier in start_command(), so it's
now a dangling pointer.

setup_pager() is then called a second time, from cmd_log_init_finish()
in this case, and any further operations using its .argv, e.g. strvec_*,
will use the dangling pointer and eventually crash. According to trivial
tests, setup_pager() is not called twice if the first call is
successful.

This patch makes sure that pager_process is properly initialized on
setup_pager(). Drop CHILD_PROCESS_INIT from its declaration since it's
no longer really necessary.

Add a test to catch possible regressions.

Reproducer:
$ git config pager.show INVALID_PAGER
$ git show $VALID_COMMIT
error: cannot run INVALID_PAGER: No such file or directory
[1]    3619 segmentation fault (core dumped)  git show $VALID_COMMIT

Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Enzo Matsumiya 2021-11-24 21:02:39 -03:00 коммит произвёл Junio C Hamano
Родитель e9d7761bb9
Коммит f917f57f40
2 изменённых файлов: 8 добавлений и 1 удалений

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@ -8,7 +8,7 @@
#define DEFAULT_PAGER "less"
#endif
static struct child_process pager_process = CHILD_PROCESS_INIT;
static struct child_process pager_process;
static const char *pager_program;
/* Is the value coming back from term_columns() just a guess? */
@ -124,6 +124,8 @@ void setup_pager(void)
setenv("GIT_PAGER_IN_USE", "true", 1);
child_process_init(&pager_process);
/* spawn the pager */
prepare_pager_args(&pager_process, pager);
pager_process.in = -1;

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@ -786,4 +786,9 @@ test_expect_success TTY 'git returns SIGPIPE on propagated signals from pager' '
test_path_is_file pager-used
'
test_expect_success TTY 'non-existent pager doesnt cause crash' '
test_config pager.show invalid-pager &&
test_terminal git show
'
test_done