mirror of
https://github.com/topjohnwu/ndk-busybox.git
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438 lines
14 KiB
Plaintext
438 lines
14 KiB
Plaintext
Why an applet can't be NOFORK or NOEXEC?
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Why can't be NOFORK:
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interactive: may wait for user input, ^C has to work
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spawner: "tool PROG ARGS" which changes program state and execs - must fork
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changes state: e.g. environment, signal handlers
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leaks: does not free allocated memory or opened fds
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alloc+xfunc: xmalloc, then xfunc - leaks memory if xfunc dies
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open+xfunc: opens fd, then calls xfunc - fd is leaked if xfunc dies
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talks to network/serial/etc: it's not known how long the delay can be,
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it's reasonable to expect it might be many seconds
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(even if usually it is not), so ^C has to work
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runner: sometimes may run for long(ish) time, and/or works with network:
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^C has to work (cat BIGFILE, chmod -R, ftpget, nc)
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"runners" can become eligible after shell is taught ^C to interrupt NOFORKs,
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need to be inspected that they do not fall into alloc+xfunc, open+xfunc,
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leak categories.
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Why can't be NOEXEC:
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suid: runs under different uid - must fork+exec
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if it's important that /proc/PID/cmdline and comm are correct.
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("pkill sh" killing itself before it kills real "sh" is no fun)
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Why shouldn't be NOFORK/NOEXEC:
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rare: not started often enough to bother optimizing (example: poweroff)
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daemon: runs indefinitely; these are also always fit "rare" category
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longterm: often runs for a long time (many seconds), execing makes
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memory footprint smaller
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complex: no immediately obvious reason why NOFORK wouldn't work,
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but does some non-obvoius operations (example: fuser, lsof, losetup);
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detailed audit often turns out that it's a leaker
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hardware: performs unusual hardware ops which may take long,
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or even hang due to hardware or firmware bugs
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Interesting example of "interactive" applet which is nevertheless can be
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(and is) NOEXEC is "rm". Yes, "rm -i" is interactive - but it's not that typical
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for users to keep it waiting for many minutes, whereas running "rm" in shell
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is very typical, and speeding up this common use via NOEXEC is useful.
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IOW: rm is "interactive", but not "longterm".
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Interesting example of an applet which can be NOFORK but if not,
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then should not be NOEXEC, is "usleep". As NOFORK, it amount to simply
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nanosleep()ing in the calling program (usually shell). No memory wasted.
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But if ran as NOEXEC, it would create a potentially long-term process,
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which would be taking more memory because it did not exec
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and did not free much of the copied memory of the parent
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(COW helps with this only as long as parent doesn't modify its memory).
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[ - NOFORK
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[[ - NOFORK
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acpid - daemon
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add-shell - noexec. leaks: open+xfunc
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addgroup - noexec. leaks
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adduser - noexec. leaks
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adjtimex - NOFORK
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ar - runner
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arch - NOFORK
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arp - talks to network: arp -n queries DNS
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arping - longterm
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ash - interactive, longterm
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awk - noexec. runner
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base64 - runner
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basename - NOFORK
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beep - longterm: beep -r 999999999
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blkdiscard - noexec. leaks: open+xioctl
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blkid - noexec
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blockdev - noexec. leaks fd
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bootchartd - daemon
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brctl - noexec
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bunzip2 - runner
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bzcat - runner
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bzip2 - runner
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cal - noexec. can be runner: cal -n9999
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cat - runner: cat HUGEFILE
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chat - longterm (when used as intended - talking to modem over stdin/out)
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chattr - noexec. runner
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chgrp - noexec. runner
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chmod - noexec. runner
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chown - noexec. runner
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chpasswd - longterm? (list of "user:password"s from stdin)
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chpst - noexec. spawner
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chroot - noexec. spawner
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chrt - noexec. spawner
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chvt - noexec. leaks: get_console_fd_or_die() may open a new fd, or return one of stdio fds
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cksum - noexec. runner
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clear - NOFORK
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cmp - runner
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comm - runner
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conspy - interactive, longterm
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cp - noexec. sometimes runner
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cpio - runner
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crond - daemon
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crontab - longterm (runs $EDITOR), leaks: open+xasprintf
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cryptpw - noexec. changes state: with --password-fd=N, moves N to stdin
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cttyhack - noexec. spawner
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cut - noexec. runner
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date - noexec. nofork candidate(needs to stop messing up env, free xasprintf result, not use xfuncs after xasprintf)
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dc - longterm (eats stdin if no params)
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dd - noexec. runner
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deallocvt - noexec. leaks: get_console_fd_or_die() may open a new fd, or return one of stdio fds
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delgroup - noexec. leaks
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deluser - noexec. leaks
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depmod - longterm(ish)
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devmem - hardware (access to device memory may hang)
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df - noexec. leaks: nested allocs
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dhcprelay - daemon
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diff - runner
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dirname - NOFORK
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dmesg - runner
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dnsd - daemon
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dnsdomainname - noexec. talks to network (may query DNS)
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dos2unix - noexec. runner
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dpkg - runner
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du - runner
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dumpkmap - noexec. leaks: get_console_fd_or_die() may open a new fd, or return one of stdio fds
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dumpleases - noexec. leaks: open+xread
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echo - NOFORK
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ed - interactive, longterm
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egrep - longterm runner ("CMD | egrep ..." may run indefinitely, better to exec to conserve memory)
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eject - hardware, leaks: open+ioctl_or_perror_and_die, changes state (moves fds)
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env - noexec. spawner, changes state (env)
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envdir - noexec. spawner
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envuidgid - noexec. spawner
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expand - runner
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expr - noexec. leaks: nested allocs
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factor - longterm (eats stdin if no params)
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fakeidentd - daemon
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false - NOFORK
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fatattr - noexec. leaks: open+xioctl, complex
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fbset - hardware, leaks: open+xfunc
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fbsplash - runner, longterm
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fdflush - hardware, leaks: open+ioctl_or_perror_and_die
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fdformat - hardware, longterm
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fdisk - interactive, longterm
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fgconsole - noexec. leaks: get_console_fd_or_die() may open a new fd, or return one of stdio fds
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fgrep - longterm runner ("CMD | fgrep ..." may run indefinitely, better to exec to conserve memory)
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find - noexec. runner
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findfs - suid
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flash_eraseall - hardware
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flash_lock - hardware
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flash_unlock - hardware
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flashcp - hardware
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flock - spawner, changes state (file locks), let's play safe and not be noexec
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fold - noexec. runner
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free - NOFORK
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freeramdisk - noexec. leaks: open+ioctl_or_perror_and_die
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fsck - interactive, longterm
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fsck.minix - needs ^C
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fsfreeze - noexec. leaks: open+xioctl
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fstrim - noexec. leaks: open+xioctl, find_block_device -> readdir+xstrdup
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fsync - NOFORK
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ftpd - daemon
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ftpget - runner
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ftpput - runner
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fuser - complex
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getopt - noexec. leaks: many allocs
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getty - interactive, longterm
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grep - longterm runner ("CMD | grep ..." may run indefinitely, better to exec to conserve memory)
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groups - noexec
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gunzip - runner
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gzip - runner
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halt - rare
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hd - noexec. runner
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hdparm - hardware
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head - noexec. runner
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hexdump - noexec. runner
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hexedit - interactive, longterm
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hostid - NOFORK
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hostname - noexec. talks to network (hostname -d may query DNS)
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httpd - daemon
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hush - interactive, longterm
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hwclock - hardware (xioctl(RTC_RD_TIME))
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i2cdetect - hardware
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i2cdump - hardware
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i2cget - hardware
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i2cset - hardware
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id - noexec
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ifconfig - hardware? (mem_start NN io_addr NN irq NN), leaks: xsocket+ioctl_or_perror_and_die
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ifenslave - noexec. leaks: xsocket+bb_perror_msg_and_die
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ifplugd - daemon
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inetd - daemon
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init - daemon
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inotifyd - daemon
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insmod - noexec
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install - runner
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ionice - noexec. spawner
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iostat - longterm: "iostat 1" runs indefinitely
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ip - noexec
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ipaddr - noexec
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ipcalc - noexec. ipcalc -h talks to network
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ipcrm - noexec
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ipcs - noexec
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iplink - noexec
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ipneigh - noexec
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iproute - noexec
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iprule - noexec
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iptunnel - noexec
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kbd_mode - noexec. leaks: xopen_nonblocking+xioctl
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kill - NOFORK
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killall - NOFORK
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killall5 - NOFORK
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klogd - daemon
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last - runner (I've got 1300 lines of output when tried it)
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less - interactive, longterm
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link - NOFORK
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linux32 - noexec. spawner
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linux64 - noexec. spawner
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linuxrc - daemon
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ln - noexec
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loadfont - noexec. leaks: config_open+bb_error_msg_and_die("map format")
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loadkmap - noexec. leaks: get_console_fd_or_die() may open a new fd, or return one of stdio fds
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logger - runner
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login - suid, interactive, longterm
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logname - NOFORK
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losetup - noexec. complex
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lpd - daemon
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lpq - runner
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lpr - runner
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ls - noexec. runner
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lsattr - noexec. runner
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lsmod - noexec
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lsof - complex
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lspci - noexec. too rare to bother for nofork
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lsscsi - noexec. too rare to bother for nofork
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lsusb - noexec. too rare to bother for nofork
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lzcat - runner
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lzma - runner
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lzop - runner
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lzopcat - runner
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makedevs - noexec
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makemime - runner
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man - spawner, interactive, longterm
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md5sum - noexec. runner
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mdev - daemon
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mesg - NOFORK
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microcom - interactive, longterm
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minips - noexec
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mkdir - NOFORK
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mkdosfs - needs ^C
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mke2fs - needs ^C
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mkfifo - noexec
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mkfs.ext2 - needs ^C
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mkfs.minix - needs ^C
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mkfs.vfat - needs ^C
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mknod - noexec
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mkpasswd - noexec. changes state: with --password-fd=N, moves N to stdin
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mkswap - needs ^C
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mktemp - noexec. leaks: xstrdup+concat_path_file
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modinfo - noexec
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modprobe - noexec
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more - interactive, longterm
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mount - suid
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mountpoint - noexec. leaks: option -n "print dev name": find_block_device -> readdir+xstrdup
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mpstat - longterm: "mpstat 1" runs indefinitely
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mt - hardware
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mv - noexec. sometimes runner
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nameif - noexec. openlog(), leaks: config_open2+ioctl_or_perror_and_die
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nbd-client - noexec
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nc - runner
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netstat - longterm with -c (continuous listing)
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nice - noexec. spawner
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nl - runner
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nmeter - longterm
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nohup - noexec. spawner
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nproc - NOFORK
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ntpd - daemon
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nuke - noexec
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od - runner
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openvt - longterm: spawns a child and waits for it
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partprobe - noexec. leaks: open+ioctl_or_perror_and_die(BLKRRPART)
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passwd - suid
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paste - noexec. runner
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patch - needs ^C
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pgrep - must fork+exec to get correct /proc/PID/cmdline and comm field
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pidof - must fork+exec to get correct /proc/PID/cmdline and comm field
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ping - suid, longterm
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ping6 - suid, longterm
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pipe_progress - longterm
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pivot_root - NOFORK
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pkill - must fork+exec to get correct /proc/PID/cmdline and comm field
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pmap - noexec candidate, leaks: open+xstrdup
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popmaildir - runner
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poweroff - rare
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powertop - interactive, longterm
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printenv - NOFORK
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printf - NOFORK
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ps - noexec
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pscan - talks to network
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pstree - noexec
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pwd - NOFORK
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pwdx - NOFORK
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raidautorun - noexec. very simple. leaks: open+xioctl
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rdate - talks to network
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rdev - noexec. leaks: find_block_device -> readdir+xstrdup
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readlink - NOFORK
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readprofile - reads /boot/System.map and /proc/profile, better to free more memory by execing?
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realpath - NOFORK
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reboot - rare
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reformime - runner
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remove-shell - noexec. leaks: open+xfunc
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renice - noexec. nofork candidate(uses getpwnam, is that ok?)
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reset - noexec. spawner (execs "stty")
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resize - noexec. changes state (signal handlers)
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resume - noexec
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rev - runner
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rm - noexec. rm -i interactive
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rmdir - NOFORK
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rmmod - noexec
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route - talks to network (may query DNS to convert IPs to names)
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rpm - runner
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rpm2cpio - runner
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rtcwake - longterm: puts system to sleep, optimizing this for speed is pointless
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run-init - spawner, rare, changes state (oh yes), execing may be important to free binary's inode
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run-parts - longterm
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runlevel - noexec. can be nofork if "endutxent()" is called unconditionally, but too rare to bother?
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runsv - daemon
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runsvdir - daemon
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rx - runner
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script - longterm: pumps script output from slave pty
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scriptreplay - longterm: plays back "script" saved output, sleeping as necessary.
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sed - runner
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sendmail - runner
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seq - noexec. runner
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setarch - noexec. spawner
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setconsole - noexec
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setfattr - noexec
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setfont - noexec. leaks a lot of stuff
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setkeycodes - noexec
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setlogcons - noexec
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setpriv - spawner, changes state, let's play safe and not be noexec
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setserial - noexec
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setsid - spawner, uses fork_or_rexec() [not audited to work in noexec], let's play safe and not be noexec
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setuidgid - noexec. spawner
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sha1sum - noexec. runner
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sha256sum - noexec. runner
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sha3sum - noexec. runner
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sha512sum - noexec. runner
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showkey - interactive, longterm
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shred - runner
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shuf - noexec. runner
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slattach - longterm (may sleep forever), uses bb_common_bufsiz1
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sleep - longterm. Could be nofork, if not the problem of "killall sleep" not killing it.
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smemcap - runner
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softlimit - noexec. spawner
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sort - noexec. runner
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split - runner
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ssl_client - longterm
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start-stop-daemon - not noexec: uses bb_common_bufsiz1
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stat - noexec. nofork candidate(needs fewer allocs)
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strings - runner
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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
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su - suid, spawner
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sulogin - noexec. spawner
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sum - runner
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sv - noexec. needs ^C (uses usleep(420000))
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svc - noexec. needs ^C (uses usleep(420000))
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svlogd - daemon
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swapoff - longterm: may cause memory pressure, execing is beneficial
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swapon - rare
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switch_root - spawner, rare, changes state (oh yes), execing may be important to free binary's inode
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sync - NOFORK
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sysctl - noexec. leaks: xstrdup+xmalloc_read
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syslogd - daemon
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tac - noexec. runner
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tail - runner
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tar - runner
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taskset - noexec. spawner
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tcpsvd - daemon
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tee - runner
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telnet - interactive, longterm
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telnetd - daemon
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test - NOFORK
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tftp - runner
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tftpd - daemon
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time - spawner, longterm, changes state (signals)
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timeout - spawner, longterm, changes state (signals)
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top - interactive, longterm
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touch - NOFORK
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tr - runner
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traceroute - suid, longterm
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traceroute6 - suid, longterm
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true - NOFORK
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truncate - NOFORK
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tty - NOFORK
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ttysize - NOFORK
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tunctl - noexec
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tune2fs - noexec. leaks: open+xfunc
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ubiattach - hardware
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ubidetach - hardware
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ubimkvol - hardware
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ubirename - hardware
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ubirmvol - hardware
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ubirsvol - hardware
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ubiupdatevol - hardware
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udhcpc - daemon
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udhcpd - daemon
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udpsvd - daemon
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uevent - daemon
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umount - noexec. leaks: nested xmalloc
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uname - NOFORK
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uncompress - runner
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unexpand - runner
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uniq - runner
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unix2dos - noexec. runner
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unlink - NOFORK
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unlzma - runner
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unlzop - runner
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unxz - runner
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unzip - runner
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uptime - noexec. nofork candidate(is getutxent ok?)
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users - noexec. nofork candidate(is getutxent ok?)
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usleep - NOFORK. But what about "killall usleep"?
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uudecode - runner
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uuencode - runner
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vconfig - noexec. leaks: xsocket+ioctl_or_perror_and_die
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vi - interactive, longterm
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vlock - suid
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volname - hardware (reads CDROM, this can take long-ish if need to spin up)
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w - noexec. nofork candidate(is getutxent ok?)
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wall - suid
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watch - longterm
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watchdog - daemon
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wc - runner
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wget - longterm
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which - NOFORK
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who - noexec. nofork candidate(is getutxent ok?)
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whoami - NOFORK
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whois - talks to network
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xargs - noexec. spawner
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xxd - noexec. runner
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xz - runner
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xzcat - runner
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yes - noexec. runner
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zcat - runner
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zcip - daemon
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