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tftpd: Don't consume arbitrary requests when failing to fork.

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We've already consumed one request, which is sufficient to prevent inetd from endlessly restarting us in this particular and extremely unlikely case.

Sponsored by:	Klara, Inc.
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D38967
This commit is contained in:
Dag-Erling Smørgrav 2023-03-10 13:24:44 +00:00
parent e3b4cb1b32
commit b4736c90ad
1 changed files with 12 additions and 40 deletions
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52
libexec/tftpd/tftpd.c
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@ -134,7 +134,8 @@ main(int argc, char *argv[])
struct passwd *nobody;
const char *chuser = "nobody";
char recvbuffer[MAXPKTSIZE];
int allow_ro = 1, allow_wo = 1;
int allow_ro = 1, allow_wo = 1, on = 1;
pid_t pid;
tzset(); /* syslog in localtime */
acting_as_client = 0;
@ -222,12 +223,9 @@ main(int argc, char *argv[])
umask(mask);
{
int on = 1;
if (ioctl(0, FIONBIO, &on) < 0) {
tftp_log(LOG_ERR, "ioctl(FIONBIO): %s", strerror(errno));
exit(1);
}
if (ioctl(0, FIONBIO, &on) < 0) {
tftp_log(LOG_ERR, "ioctl(FIONBIO): %s", strerror(errno));
exit(1);
}
/* Find out who we are talking to and what we are going to do */
@ -255,40 +253,14 @@ main(int argc, char *argv[])
* break before doing the above "recvfrom", inetd would
* spawn endless instances, clogging the system.
*/
{
int i, pid;
for (i = 1; i < 20; i++) {
pid = fork();
if (pid < 0) {
sleep(i);
/*
* flush out to most recently sent request.
*
* This may drop some request, but those
* will be resent by the clients when
* they timeout. The positive effect of
* this flush is to (try to) prevent more
* than one tftpd being started up to service
* a single request from a single client.
*/
peerlen = sizeof peer_sock;
i = recvfrom(0, recvbuffer, MAXPKTSIZE, 0,
(struct sockaddr *)&peer_sock, &peerlen);
if (i > 0) {
n = i;
}
} else {
break;
}
}
if (pid < 0) {
tftp_log(LOG_ERR, "fork: %s", strerror(errno));
exit(1);
} else if (pid != 0) {
exit(0);
}
pid = fork();
if (pid < 0) {
tftp_log(LOG_ERR, "fork: %s", strerror(errno));
exit(1);
} else if (pid != 0) {
exit(0);
}
/* child */
#ifdef LIBWRAP
/*