From ee69e7884e0cae3d2feabd5fcce8d3dfb44dda3a Mon Sep 17 00:00:00 2001 From: "brian m. carlson" Date: Sun, 28 Aug 2022 21:41:43 +0000 Subject: [PATCH] gc: use temporary file for editing crontab While cron is specified by POSIX, there are a wide variety of implementations in use. "git maintenance" assumes that the "crontab" command can be fed from its standard input the new contents and the syntax to do so is not to have any filename argument, as POSIX describes. However, on FreeBSD, the cron implementation requires a file name argument: if the user wants to edit standard input, they must specify "-". Unfortunately, POSIX systems do not have to interpret "-" on the command line of crontab as a request to read from the standard input. Blindly adding "-" on the command line would not work as a general solution. Since POSIX tells us that cron must accept a file name argument, let's solve this problem by specifying a temporary file instead. This will ensure that we work with the vast majority of implementations. Note that because delete_tempfile closes the file for us, we should not call fclose here on the handle, since doing so will introduce a double free. Reported-by: Renato Botelho Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano --- builtin/gc.c | 39 +++++++++++++++++++++++---------------- t/helper/test-crontab.c | 4 ++-- 2 files changed, 25 insertions(+), 18 deletions(-) diff --git a/builtin/gc.c b/builtin/gc.c index 021e9256ae..b04f1c5522 100644 --- a/builtin/gc.c +++ b/builtin/gc.c @@ -2059,6 +2059,7 @@ static int crontab_update_schedule(int run_maintenance, int fd) struct child_process crontab_edit = CHILD_PROCESS_INIT; FILE *cron_list, *cron_in; struct strbuf line = STRBUF_INIT; + struct tempfile *tmpedit = NULL; get_schedule_cmd(&cmd, NULL); strvec_split(&crontab_list.args, cmd); @@ -2073,6 +2074,17 @@ static int crontab_update_schedule(int run_maintenance, int fd) /* Ignore exit code, as an empty crontab will return error. */ finish_command(&crontab_list); + tmpedit = mks_tempfile_t(".git_cron_edit_tmpXXXXXX"); + if (!tmpedit) { + result = error(_("failed to create crontab temporary file")); + goto out; + } + cron_in = fdopen_tempfile(tmpedit, "w"); + if (!cron_in) { + result = error(_("failed to open temporary file")); + goto out; + } + /* * Read from the .lock file, filtering out the old * schedule while appending the new schedule. @@ -2080,19 +2092,6 @@ static int crontab_update_schedule(int run_maintenance, int fd) cron_list = fdopen(fd, "r"); rewind(cron_list); - strvec_split(&crontab_edit.args, cmd); - crontab_edit.in = -1; - crontab_edit.git_cmd = 0; - - if (start_command(&crontab_edit)) - return error(_("failed to run 'crontab'; your system might not support 'cron'")); - - cron_in = fdopen(crontab_edit.in, "w"); - if (!cron_in) { - result = error(_("failed to open stdin of 'crontab'")); - goto done_editing; - } - while (!strbuf_getline_lf(&line, cron_list)) { if (!in_old_region && !strcmp(line.buf, BEGIN_LINE)) in_old_region = 1; @@ -2126,14 +2125,22 @@ static int crontab_update_schedule(int run_maintenance, int fd) } fflush(cron_in); - fclose(cron_in); - close(crontab_edit.in); -done_editing: + strvec_split(&crontab_edit.args, cmd); + strvec_push(&crontab_edit.args, get_tempfile_path(tmpedit)); + crontab_edit.git_cmd = 0; + + if (start_command(&crontab_edit)) { + result = error(_("failed to run 'crontab'; your system might not support 'cron'")); + goto out; + } + if (finish_command(&crontab_edit)) result = error(_("'crontab' died")); else fclose(cron_list); +out: + delete_tempfile(&tmpedit); return result; } diff --git a/t/helper/test-crontab.c b/t/helper/test-crontab.c index e7c0137a47..2942543046 100644 --- a/t/helper/test-crontab.c +++ b/t/helper/test-crontab.c @@ -17,8 +17,8 @@ int cmd__crontab(int argc, const char **argv) if (!from) return 0; to = stdout; - } else if (argc == 2) { - from = stdin; + } else if (argc == 3) { + from = fopen(argv[2], "r"); to = fopen(argv[1], "w"); } else return error("unknown arguments");