commit a22fbab98690f802ae3bda276078cc7fc767feba Author: teor teor@torproject.org Date: Wed Sep 4 15:38:58 2019 +1000

log: Don't close file log fds that are being used by the err module

Instead, dup() file log fds, before passing them to the err module.

Closes 31613, part of 31594. --- src/lib/err/torerr.c | 6 ++++++ src/lib/log/log.c | 43 ++++++++++++++++++++++++++++++++++--------- 2 files changed, 40 insertions(+), 9 deletions(-)

diff --git a/src/lib/err/torerr.c b/src/lib/err/torerr.c index 2c4a10a5b..f460fd837 100644 --- a/src/lib/err/torerr.c +++ b/src/lib/err/torerr.c @@ -111,6 +111,12 @@ tor_log_get_sigsafe_err_fds(const int **out) * other emergency condition. Ignore any beyond the first * TOR_SIGSAFE_LOG_MAX_FDS. * + * These fds must remain open even after the log module has shut down. (And + * they should remain open even while logs are being reconfigured.) Therefore, + * any fds closed by the log module should be dup()ed, and the duplicate fd + * should be given to the err module in fds. In particular, the log module + * closes the file log fds, but does not close the stdio log fds. + * * If fds is NULL or n is 0, clears the list of error fds. */ void diff --git a/src/lib/log/log.c b/src/lib/log/log.c index d21d8d1d4..2214d4b59 100644 --- a/src/lib/log/log.c +++ b/src/lib/log/log.c @@ -664,13 +664,24 @@ tor_log_update_sigsafe_err_fds(void) const logfile_t *lf; int found_real_stderr = 0;

- int fds[TOR_SIGSAFE_LOG_MAX_FDS]; + /* log_fds and err_fds contain matching entries: log_fds are the fds used by + * the log module, and err_fds are the fds used by the err module. + * For stdio logs, the log_fd and err_fd values are identical, + * and the err module closes the fd on shutdown. + * For file logs, the err_fd is a dup() of the log_fd, + * and the log and err modules both close their respective fds on shutdown. + * (Once all fds representing a file are closed, the underlying file is + * closed.) + */ + int log_fds[TOR_SIGSAFE_LOG_MAX_FDS]; + int err_fds[TOR_SIGSAFE_LOG_MAX_FDS]; int n_fds;

LOCK_LOGS(); /* Reserve the first one for stderr. This is safe because when we daemonize, - * we dup2 /dev/null to stderr, */ - fds[0] = STDERR_FILENO; + * we dup2 /dev/null to stderr. + * For stderr, log_fds and err_fds are the same. */ + log_fds[0] = err_fds[0] = STDERR_FILENO; n_fds = 1;

for (lf = logfiles; lf; lf = lf->next) { @@ -684,25 +695,39 @@ tor_log_update_sigsafe_err_fds(void) (LD_BUG|LD_GENERAL)) { if (lf->fd == STDERR_FILENO) found_real_stderr = 1; - /* Avoid duplicates */ - if (int_array_contains(fds, n_fds, lf->fd)) + /* Avoid duplicates by checking the log module fd against log_fds */ + if (int_array_contains(log_fds, n_fds, lf->fd)) continue; - fds[n_fds++] = lf->fd; + /* Update log_fds using the log module's fd */ + log_fds[n_fds] = lf->fd; + if (lf->needs_close) { + /* File log fds are duplicated, because close_log() closes the log + * module's fd, and tor_log_close_sigsafe_err_fds() closes the err + * module's fd. Both refer to the same file. */ + err_fds[n_fds] = dup(lf->fd); + } else { + /* stdio log fds are not closed by the log module. + * tor_log_close_sigsafe_err_fds() closes stdio logs. */ + err_fds[n_fds] = lf->fd; + } + n_fds++; if (n_fds == TOR_SIGSAFE_LOG_MAX_FDS) break; } }

if (!found_real_stderr && - int_array_contains(fds, n_fds, STDOUT_FILENO)) { + int_array_contains(log_fds, n_fds, STDOUT_FILENO)) { /* Don't use a virtual stderr when we're also logging to stdout. */ raw_assert(n_fds >= 2); /* Don't tor_assert inside log fns */ - fds[0] = fds[--n_fds]; + --n_fds; + log_fds[0] = log_fds[n_fds]; + err_fds[0] = err_fds[n_fds]; }

UNLOCK_LOGS();

- tor_log_set_sigsafe_err_fds(fds, n_fds); + tor_log_set_sigsafe_err_fds(err_fds, n_fds); }

/** Add to <b>out</b> a copy of every currently configured log file name. Used