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author | Lennart Poettering <lennart@poettering.net> | 2017-12-22 13:08:14 +0100 |
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committer | Lennart Poettering <lennart@poettering.net> | 2017-12-25 11:48:21 +0100 |
commit | 4c253ed1cae8b4df72ce1353ee826a4fae399e25 (patch) | |
tree | 5fc52b199a402b4ddaae0e3005fa85cc610c377f /src/shared/pager.c | |
parent | d8caff6db672ab0f2d8064c61f5ef0e8e8d288ca (diff) | |
download | systemd-4c253ed1cae8b4df72ce1353ee826a4fae399e25.tar.gz |
tree-wide: introduce new safe_fork() helper and port everything over
This adds a new safe_fork() wrapper around fork() and makes use of it
everywhere. The new wrapper does a couple of things we previously did
manually and separately in a safer, more correct and automatic way:
1. Optionally resets signal handlers/mask in the child
2. Sets a name on all processes we fork off right after forking off (and
the patch assigns useful names for all processes we fork off now,
following a systematic naming scheme: always enclosed in () – in order
to indicate that these are not proper, exec()ed processes, but only
forked off children, and if the process is long-running with only our
own code, without execve()'ing something else, it gets am "sd-" prefix.)
3. Optionally closes all file descriptors in the child
4. Optionally sets a PR_SET_DEATHSIG to SIGTERM in the child, in a safe
way so that the parent dying before this happens being handled
safely.
5. Optionally reopens the logs
6. Optionally connects stdin/stdout/stderr to /dev/null
7. Debug logs about the forked off processes.
Diffstat (limited to 'src/shared/pager.c')
-rw-r--r-- | src/shared/pager.c | 47 |
1 files changed, 10 insertions, 37 deletions
diff --git a/src/shared/pager.c b/src/shared/pager.c index 39997278f1..17e0121a66 100644 --- a/src/shared/pager.c +++ b/src/shared/pager.c @@ -62,7 +62,7 @@ static bool stderr_redirected = false; int pager_open(bool no_pager, bool jump_to_end) { _cleanup_close_pair_ int fd[2] = { -1, -1 }; const char *pager; - pid_t parent_pid; + int r; if (no_pager) return 0; @@ -89,18 +89,13 @@ int pager_open(bool no_pager, bool jump_to_end) { if (pipe2(fd, O_CLOEXEC) < 0) return log_error_errno(errno, "Failed to create pager pipe: %m"); - parent_pid = getpid_cached(); - - pager_pid = fork(); - if (pager_pid < 0) - return log_error_errno(errno, "Failed to fork pager: %m"); - - /* In the child start the pager */ - if (pager_pid == 0) { + r = safe_fork("(pager)", FORK_RESET_SIGNALS|FORK_DEATHSIG, &pager_pid); + if (r < 0) + return log_error_errno(r, "Failed to fork pager: %m"); + if (r == 0) { const char* less_opts, *less_charset; - (void) reset_all_signal_handlers(); - (void) reset_signal_mask(); + /* In the child start the pager */ (void) dup2(fd[0], STDIN_FILENO); safe_close_pair(fd); @@ -124,15 +119,6 @@ int pager_open(bool no_pager, bool jump_to_end) { setenv("LESSCHARSET", less_charset, 1) < 0) _exit(EXIT_FAILURE); - /* Make sure the pager goes away when the parent dies */ - if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0) - _exit(EXIT_FAILURE); - - /* Check whether our parent died before we were able - * to set the death signal */ - if (getppid() != parent_pid) - _exit(EXIT_SUCCESS); - if (pager) { execlp(pager, pager, NULL); execl("/bin/sh", "sh", "-c", pager, NULL); @@ -222,24 +208,11 @@ int show_man_page(const char *desc, bool null_stdio) { } else args[1] = desc; - pid = fork(); - if (pid < 0) - return log_error_errno(errno, "Failed to fork: %m"); - - if (pid == 0) { + r = safe_fork("(man)", FORK_RESET_SIGNALS|FORK_DEATHSIG|(null_stdio ? FORK_NULL_STDIO : 0), &pid); + if (r < 0) + return log_error_errno(r, "Failed to fork: %m"); + if (r == 0) { /* Child */ - - (void) reset_all_signal_handlers(); - (void) reset_signal_mask(); - - if (null_stdio) { - r = make_null_stdio(); - if (r < 0) { - log_error_errno(r, "Failed to kill stdio: %m"); - _exit(EXIT_FAILURE); - } - } - execvp(args[0], (char**) args); log_error_errno(errno, "Failed to execute man: %m"); _exit(EXIT_FAILURE); |