Why an applet can't be NOFORK or NOEXEC?

Why can't be NOFORK:
interactive: may wait for user input, ^C has to work
spawner: "tool PROG ARGS" which changes program state and execs - must fork
changes state: e.g. environment, signal handlers
alloc+xfunc: xmalloc, then xfunc - leaks memory if xfunc dies
open+xfunc: opens fd, then calls xfunc - fd is leaked if xfunc dies
leaks: does not free allocated memory or opened fds
runner: sometimes may run for long(ish) time, and/or works with network:
	^C has to work (cat BIGFILE, chmod -R, ftpget, nc)

"runners" can become eligible after shell is taught ^C to interrupt NOFORKs,
need to be inspected that they do not fall into alloc+xfunc, open+xfunc,
leak categories.

Why can't be NOEXEC:
suid: runs under different uid - must fork+exec

Why shouldn't be NOFORK/NOEXEC:
rare: not started often enough to bother optimizing (example: poweroff)
daemon: runs indefinitely; these are also always fit "rare" category
longterm: often runs for a long time (many seconds), execing makes
	memory footprint smaller
complex: no immediately obvious reason why NOFORK wouldn't work,
	but does some non-obvoius operations (example: fuser, lsof, losetup);
	detailed audit often turns out that it's a leaker

Interesting example of "interactive" applet which is nevertheless can be
(and is) NOEXEC is "rm". Yes, "rm -i" is interactive - but it's not that typical
for users to keep it waiting for many minutes, whereas running "rm" in shell
is very typical, and speeding up this common use via NOEXEC is useful.
IOW: rm is "interactive", but not "longterm".


[ - NOFORK
[[ - NOFORK
acpid - daemon
add-shell
addgroup
adduser
adjtimex - NOFORK
ar - runner
arch - NOFORK
arp - complex, rare
arping - runner
ash - interactive, longterm
awk - noexec. runner
base64 - runner
basename - NOFORK
beep
blkdiscard
blkid
blockdev - noexec. leaks fd
bootchartd - daemon
brctl
bunzip2 - runner
busybox
bzcat - runner
bzip2 - runner
cal - runner: cal -n9999
cat - runner
chat - needs ^C to work
chattr - noexec. runner
chgrp - noexec. runner
chmod - noexec. runner
chown - noexec. runner
chpasswd - runner (list of "user:password"s from stdin)
chpst - noexec. spawner
chroot - noexec. spawner
chrt - noexec. spawner
chvt - noexec. leaks: get_console_fd_or_die() may open a new fd, or return one of stdio fds
cksum - noexec. runner
clear - NOFORK
cmp - runner
comm - runner
conspy - interactive, longterm
cp - noexec. runner
cpio - runner
crond - daemon
crontab - longterm (runs $EDITOR), leaks: open+xasprintf
cryptpw - noexec. changes state: with --password-fd=N, moves N to stdin
cttyhack - noexec. spawner
cut - noexec. runner
date - noexec. nofork candidate(needs to stop messing up env, free xasprintf result, not use xfuncs after xasprintf)
dc - runner (eats stdin if no params)
dd - noexec. runner
deallocvt - noexec. leaks: get_console_fd_or_die() may open a new fd, or return one of stdio fds
delgroup
deluser
depmod - complex, rare
devmem - runner, complex (access to device memory may hang)
df - leaks: nested allocs
dhcprelay - daemon
diff - runner
dirname - NOFORK
dmesg - runner
dnsd - daemon
dnsdomainname - needs ^C (may talk to DNS servers, which may be down)
dos2unix - noexec. runner
dpkg - runner
du - runner
dumpkmap - noexec. leaks: get_console_fd_or_die() may open a new fd, or return one of stdio fds
dumpleases - leaks: open+xread
echo - NOFORK
ed - interactive, longterm
egrep - longterm runner ("CMD | egrep ..."  may run indefinitely, better to exec to conserve memory)
eject - leaks: open+ioctl_or_perror_and_die, changes state (moves fds)
env - noexec. spawner, changes state (env)
envdir - noexec. spawner
envuidgid - noexec. spawner
expand - runner
expr - leaks: nested allocs
factor - runner (eats stdin if no params)
fakeidentd - daemon
false - NOFORK
fatattr - leaks: open+xioctl, complex
fbset - leaks: open+xfunc, complex, rare
fbsplash - runner, longterm
fdflush - leaks: open+ioctl_or_perror_and_die, needs ^C (floppy may be unresponsive), rare
fdformat - needs ^C (floppy may be unresponsive), longterm, rare
fdisk - interactive, longterm
fgconsole - noexec. leaks: get_console_fd_or_die() may open a new fd, or return one of stdio fds
fgrep - longterm runner ("CMD | fgrep ..."  may run indefinitely, better to exec to conserve memory)
find - noexec. runner
findfs - suid
flash_eraseall
flash_lock
flash_unlock
flashcp
flock - spawner, changes state (file locks), let's play safe and not be noexec
fold - noexec. runner
free - nofork candidate(struct globals, needs to close /proc/meminfo fd)
freeramdisk - leaks: open+ioctl_or_perror_and_die
fsck - interactive, longterm
fsck.minix - needs ^C
fsfreeze - noexec. leaks: open+xioctl
fstrim - noexec. leaks: open+xioctl, find_block_device -> readdir+xstrdup
fsync - NOFORK
ftpd - daemon
ftpget - runner
ftpput - runner
fuser - complex
getopt - noexec. leaks: many allocs
getty - interactive, longterm
grep - longterm runner ("CMD | grep ..."  may run indefinitely, better to exec to conserve memory)
groups - noexec
gunzip - runner
gzip - runner
halt - rare
hd - noexec. runner
hdparm - complex, rare
head - noexec. runner
hexdump - noexec. runner
hostid - NOFORK
hostname - needs ^C (may talk to DNS servers, which may be down)
httpd - daemon
hush - interactive, longterm
hwclock - talks to hardware (xioctl(RTC_RD_TIME)) - needs ^C
i2cdetect
i2cdump
i2cget
i2cset
id - noexec
ifconfig - leaks: xsocket+ioctl_or_perror_and_die
ifenslave - leaks: xsocket+bb_perror_msg_and_die
ifplugd - daemon
inetd - daemon
init - daemon
inotifyd - daemon
insmod - noexec
install - runner
ionice - noexec. spawner
iostat - runner
ip - noexec candidate
ipaddr - noexec candidate
ipcalc - noexec candidate
ipcrm - noexec candidate
ipcs - noexec candidate
iplink - noexec candidate
ipneigh - noexec candidate
iproute - noexec candidate
iprule - noexec candidate
iptunnel - noexec candidate
kbd_mode - noexec. leaks: xopen_nonblocking+xioctl
kill - NOFORK
killall - NOFORK
killall5 - NOFORK
klogd - daemon
last - runner (I've got 1300 lines of output when tried it)
less - interactive, longterm
link - NOFORK
linux32 - noexec. spawner
linux64 - noexec. spawner
linuxrc - daemon
ln - noexec
loadfont - noexec. leaks: config_open+bb_error_msg_and_die("map format")
loadkmap - noexec. leaks: get_console_fd_or_die() may open a new fd, or return one of stdio fds
logger - runner
login - suid, interactive, longterm
logname - NOFORK
losetup - complex
lpd - daemon
lpq - runner
lpr - runner
ls - noexec. runner
lsattr - noexec. runner
lsmod - noexec
lsof - complex
lspci - noexec. too rare to bother for nofork
lsscsi - noexec. too rare to bother for nofork
lsusb - noexec. too rare to bother for nofork
lzcat - runner
lzma - runner
lzop - runner
lzopcat - runner
makedevs
makemime - runner
man - spawner, interactive, longterm
md5sum - noexec. runner
mdev - daemon
mesg - NOFORK
microcom - interactive, longterm
mkdir - NOFORK
mkdosfs - needs ^C
mke2fs - needs ^C
mkfifo - noexec
mkfs.ext2 - needs ^C
mkfs.minix - needs ^C
mkfs.vfat - needs ^C
mknod - noexec
mkpasswd - noexec. changes state: with --password-fd=N, moves N to stdin
mkswap - needs ^C
mktemp - noexec. leaks: xstrdup+concat_path_file
modinfo - noexec
modprobe - noexec
more - interactive, longterm
mount - suid
mountpoint - noexec. leaks: option -n "print dev name": find_block_device -> readdir+xstrdup
mpstat - longterm: "mpstat 1" runs indefinitely
mt - rare
mv - noexec candidate, runner
nameif - noexec. openlog(), leaks: config_open2+ioctl_or_perror_and_die
nbd-client
nc - runner
netstat - runner with -c
nice - noexec. spawner
nl - runner
nmeter - longterm
nohup - noexec. spawner
nproc - NOFORK
ntpd - daemon
od - runner
openvt - longterm: spawns a child and waits for it
partprobe - noexec. leaks: open+ioctl_or_perror_and_die(BLKRRPART)
passwd - suid
paste - noexec. runner
patch - needs ^C
pgrep - nofork candidate(xregcomp, procps_scan - are they ok?)
pidof - nofork candidate(uses find_pid_by_name, is that ok?)
ping - suid, runner
ping6 - suid, runner
pipe_progress - longterm
pivot_root - NOFORK
pkill - nofork candidate(xregcomp, procps_scan - are they ok?)
pmap - noexec candidate, leaks: open+xstrdup
popmaildir - runner
poweroff - rare
powertop - interactive, longterm
printenv - NOFORK
printf - NOFORK
ps - looks for AT_CLKTCK elf aux vector, therefore can't be noexec
pscan - longterm
pstree - noexec
pwd - NOFORK
pwdx - NOFORK
raidautorun - noexec. very simple. leaks: open+xioctl
rdate - needs ^C (may talk to DNS servers, which may be down)
rdev - leaks: find_block_device -> readdir+xstrdup
readlink - NOFORK
readprofile
realpath - NOFORK
reboot - rare
reformime - runner
remove-shell
renice - nofork candidate(uses getpwnam, is that ok?)
reset - noexec. spawner (execs "stty")
resize - noexec. changes state (signal handlers)
rev - runner
rm - noexec. rm -i interactive
rmdir - NOFORK
rmmod - noexec
route - needs ^C (may talk to DNS servers, which may be down)
rpm - runner
rpm2cpio - runner
rtcwake - longterm: puts system to sleep, optimizing this for speed is pointless
run-parts - longterm
runlevel - noexec. can be nofork if "endutxent()" is called unconditionally, but too rare to bother?
runsv - daemon
runsvdir - daemon
rx - runner
script
scriptreplay
sed - runner
sendmail - runner
seq - noexec. runner
setarch - noexec. spawner
setconsole - noexec
setfont - noexec. leaks a lot of stuff
setkeycodes - noexec
setlogcons - noexec
setpriv - spawner, changes state, let's play safe and not be noexec
setserial - noexec
setsid - spawner, uses fork_or_rexec() [not audited to work in noexec], let's play safe and not be noexec
setuidgid - noexec. spawner
sha1sum - noexec. runner
sha256sum - noexec. runner
sha3sum - noexec. runner
sha512sum - noexec. runner
showkey - interactive, longterm
shred - runner
shuf - noexec. runner
slattach - longterm (may sleep forever), uses bb_common_bufsiz1
sleep - runner, longterm
smemcap - runner
softlimit - noexec. spawner
sort - noexec. runner
split - runner
ssl_client - longterm
start-stop-daemon
stat - nofork candidate(needs fewer allocs)
strings - runner
stty - noexec. nofork candidate: has no allocs or opens except xmove_fd(xopen("-F DEVICE"),STDIN). tcsetattr(STDIN) is not a problem: it would work the same across processes sharing this fd
su - suid, spawner
sulogin - noexec. spawner
sum - runner
sv - noexec. needs ^C (uses usleep(420000))
svc - noexec. needs ^C (uses usleep(420000))
svlogd - daemon
swapoff - rare
swapon - rare
switch_root - spawner, rare, changes state (oh yes), execing may be important to free binary's inode
sync - NOFORK
sysctl - noexec. leaks: xstrdup+xmalloc_read
syslogd - daemon
tac - noexec. runner
tail - runner
tar - runner
taskset - noexec. spawner
tcpsvd - daemon
tee - runner
telnet - interactive, longterm
telnetd - daemon
test - NOFORK
tftp - runner
tftpd - daemon
time - spawner, longterm, changes state (signals)
timeout - spawner, longterm, changes state (signals)
top - interactive, longterm
touch - NOFORK
tr - runner
traceroute - suid, runner
traceroute6 - suid, runner
true - NOFORK
truncate - NOFORK
tty - NOFORK
ttysize - NOFORK
tunctl - noexec
tune2fs - noexec. leaks: open+xfunc
ubiattach
ubidetach
ubimkvol
ubirename
ubirmvol
ubirsvol
ubiupdatevol
udhcpc - daemon
udhcpd - daemon
udpsvd - daemon
uevent - daemon
umount - noexec. leaks: nested xmalloc
uname - NOFORK
uncompress - runner
unexpand - runner
uniq - runner
unix2dos - noexec. runner
unlink - NOFORK
unlzma - runner
unlzop - runner
unxz - runner
unzip - runner
uptime - nofork candidate(is getutxent ok?)
users - nofork candidate(is getutxent ok?)
usleep - NOFORK
uudecode - runner
uuencode - runner
vconfig - leaks: xsocket+ioctl_or_perror_and_die
vi - interactive, longterm
vlock - suid
volname - runner
w - nofork candidate(is getutxent ok?)
wall - suid
watch - longterm
watchdog - daemon
wc - runner
wget - longterm
which - NOFORK
who - nofork candidate(is getutxent ok?)
whoami - NOFORK
whois - needs ^C
xargs - noexec. spawner
xxd - noexec. runner
xz - runner
xzcat - runner
yes - noexec. runner
zcat - runner
zcip - daemon