Hi Mike,
For which version of ppp package did you do this patch? Is it for 2.4.4 or
it is for the mainline source?
I am using a ppp package (2.4.4) from uClinux distribution, but I just
wondered the difference of your patch.
Regards,
Murat
Mike Frysinger wrote:
>
> Running Linux on a no-mmu processor requires a few considerations. In the
> case of ppp, we cannot fork(), nor can the child return from the function
> it forks, nor can the child free up shared memory.
>
> This patch boils down to:
> - a new -DNOMMU flag
> - do not free memory in child
> - do not return from forked function ... pass in function and its
> arguments for the child to call itself
> - call _exit() rather than exit()
>
> Signed-off-by: Mike Frysinger <vapier@xxxxxxxxxx>
> ---
> pppd/main.c | 110
> +++++++++++++++++++++++++++++++++++++++-------------------
> pppd/tdb.c | 4 ++
> 2 files changed, 78 insertions(+), 36 deletions(-)
>
> diff --git a/pppd/main.c b/pppd/main.c
> index 4e1952b..565acb2 100644
> --- a/pppd/main.c
> +++ b/pppd/main.c
> @@ -1537,8 +1537,12 @@ bad_signal(sig)
> * This also arranges for the specified fds to be dup'd to
> * fds 0, 1, 2 in the child.
> */
> +struct child_tail {
> + void (*followup)(void *args);
> + void *args;
> +};
> pid_t
> -safe_fork(int infd, int outfd, int errfd)
> +safe_fork_tail(int infd, int outfd, int errfd, struct child_tail *tail)
> {
> pid_t pid;
> int fd, pipefd[2];
> @@ -1554,7 +1558,11 @@ safe_fork(int infd, int outfd, int errfd)
>
> if (pipe(pipefd) == -1)
> pipefd[0] = pipefd[1] = -1;
> +#ifdef NOMMU
> + pid = vfork();
> +#else
> pid = fork();
> +#endif
> if (pid < 0) {
> error("fork failed: %m");
> return -1;
> @@ -1612,14 +1620,36 @@ safe_fork(int infd, int outfd, int errfd)
> /* this close unblocks the read() call above in the parent */
> close(pipefd[1]);
>
> + if (tail)
> + tail->followup(tail->args);
> return 0;
> }
> +pid_t
> +safe_fork(int infd, int outfd, int errfd)
> +{
> + return safe_fork_tail(infd, outfd, errfd, NULL);
> +}
>
> /*
> * device_script - run a program to talk to the specified fds
> * (e.g. to run the connector or disconnector script).
> * stderr gets connected to the log fd or to the _PATH_CONNERRS file.
> */
> +void device_script_tail(void *args)
> +{
> + char *program = args;
> + /* here we are executing in the child */
> +
> + setgid(getgid());
> + setuid(uid);
> + if (getuid() != uid) {
> + fprintf(stderr, "pppd: setuid failed\n");
> + _exit(1);
> + }
> + execl("/bin/sh", "sh", "-c", program, (char *)0);
> + perror("pppd: could not exec /bin/sh");
> + _exit(99);
> +}
> int
> device_script(program, in, out, dont_wait)
> char *program;
> @@ -1629,6 +1659,7 @@ device_script(program, in, out, dont_wait)
> int pid;
> int status = -1;
> int errfd;
> + struct child_tail tail = { device_script_tail, program };
>
> if (log_to_fd >= 0)
> errfd = log_to_fd;
> @@ -1636,7 +1667,7 @@ device_script(program, in, out, dont_wait)
> errfd = open(_PATH_CONNERRS, O_WRONLY | O_APPEND | O_CREAT, 0600);
>
> ++conn_running;
> - pid = safe_fork(in, out, errfd);
> + pid = safe_fork_tail(in, out, errfd, &tail);
>
> if (pid != 0 && log_to_fd < 0)
> close(errfd);
> @@ -1662,17 +1693,7 @@ device_script(program, in, out, dont_wait)
> return (status == 0 ? 0 : -1);
> }
>
> - /* here we are executing in the child */
> -
> - setgid(getgid());
> - setuid(uid);
> - if (getuid() != uid) {
> - fprintf(stderr, "pppd: setuid failed\n");
> - exit(1);
> - }
> - execl("/bin/sh", "sh", "-c", program, (char *)0);
> - perror("pppd: could not exec /bin/sh");
> - exit(99);
> + _exit(99);
> /* NOTREACHED */
> }
>
> @@ -1687,6 +1708,43 @@ device_script(program, in, out, dont_wait)
> * If done != NULL, (*done)(arg) will be called later (within
> * reap_kids) iff the return value is > 0.
> */
> +struct run_program_args {
> + char *prog;
> + char **args;
> + int must_exist;
> +};
> +void
> +run_program_tail(void *vargs)
> +{
> + struct run_program_args *rpargs = vargs;
> + char *prog = rpargs->prog;
> + char **args = rpargs->args;
> + int must_exist = rpargs->must_exist;
> +
> + /* Leave the current location */
> + (void) setsid(); /* No controlling tty. */
> + (void) umask (S_IRWXG|S_IRWXO);
> + (void) chdir ("/"); /* no current directory. */
> + setuid(0); /* set real UID = root */
> + setgid(getegid());
> +
> +#ifdef BSD
> + /* Force the priority back to zero if pppd is running higher. */
> + if (setpriority (PRIO_PROCESS, 0, 0) < 0)
> + warn("can't reset priority to 0: %m");
> +#endif
> +
> + /* run the program */
> + execve(prog, args, script_env);
> + if (must_exist || errno != ENOENT) {
> + /* have to reopen the log, there's nowhere else
> + for the message to go. */
> + reopen_log();
> + syslog(LOG_ERR, "Can't execute %s: %m", prog);
> + closelog();
> + }
> + _exit(-1);
> +}
> pid_t
> run_program(prog, args, must_exist, done, arg, wait)
> char *prog;
> @@ -1698,6 +1756,8 @@ run_program(prog, args, must_exist, done, arg, wait)
> {
> int pid, status;
> struct stat sbuf;
> + struct run_program_args vargs = { prog, args, must_exist };
> + struct child_tail tail = { run_program_tail, &vargs };
>
> /*
> * First check if the file exists and is executable.
> @@ -1713,7 +1773,7 @@ run_program(prog, args, must_exist, done, arg, wait)
> return 0;
> }
>
> - pid = safe_fork(fd_devnull, fd_devnull, fd_devnull);
> + pid = safe_fork_tail(fd_devnull, fd_devnull, fd_devnull, &tail);
> if (pid == -1) {
> error("Failed to create child process for %s: %m", prog);
> return -1;
> @@ -1733,28 +1793,6 @@ run_program(prog, args, must_exist, done, arg,
> wait)
> return pid;
> }
>
> - /* Leave the current location */
> - (void) setsid(); /* No controlling tty. */
> - (void) umask (S_IRWXG|S_IRWXO);
> - (void) chdir ("/"); /* no current directory. */
> - setuid(0); /* set real UID = root */
> - setgid(getegid());
> -
> -#ifdef BSD
> - /* Force the priority back to zero if pppd is running higher. */
> - if (setpriority (PRIO_PROCESS, 0, 0) < 0)
> - warn("can't reset priority to 0: %m");
> -#endif
> -
> - /* run the program */
> - execve(prog, args, script_env);
> - if (must_exist || errno != ENOENT) {
> - /* have to reopen the log, there's nowhere else
> - for the message to go. */
> - reopen_log();
> - syslog(LOG_ERR, "Can't execute %s: %m", prog);
> - closelog();
> - }
> _exit(-1);
> }
>
> diff --git a/pppd/tdb.c b/pppd/tdb.c
> index bdc5828..7ff431e 100644
> --- a/pppd/tdb.c
> +++ b/pppd/tdb.c
> @@ -1866,6 +1866,9 @@ TDB_CONTEXT *tdb_open_ex(const char *name, int
> hash_size, int tdb_flags,
> **/
> int tdb_close(TDB_CONTEXT *tdb)
> {
> +#ifdef NOMMU
> + return close(tdb->fd);
> +#else
> TDB_CONTEXT **i;
> int ret = 0;
>
> @@ -1892,6 +1895,7 @@ int tdb_close(TDB_CONTEXT *tdb)
> SAFE_FREE(tdb);
>
> return ret;
> +#endif
> }
>
> /* lock/unlock entire database */
> --
> 1.6.4
>
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