7f9d62d7f
Denys Vlasenko
2017-08-04
Subject
tweak NOFORK_NOEXEC.lst
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NOFORK_NOEXEC.lst+11 -9
| @@ -2,26 +2,28 @@ 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's environment - must fork |
| + | 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! |
| + | "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 |
| + | categories. |
| Why can't be NOEXEC: | |
| suid: runs under different uid - must fork+exec | |
| Why shouldn't be NOFORK/NOEXEC: | |
| - | complex: no immediately obvious reason why NOFORK wouldn't work, |
| - | but does some non-obvoius operations (example: fuser, lsof, losetup); |
| - | nested xmallocs (typical in complex code) is a problem for NOFORK |
| - | rare: not used often enough to bother optimizing (example: poweroff) |
| + | 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 would make | |
| memory footprint smaller | |
| - | daemon: runs indefinitely |
| + | complex: no immediately obvious reason why NOFORK wouldn't work, |
| + | but does some non-obvoius operations (example: fuser, lsof, losetup) |
| [ - NOFORK | |
| [[ - NOFORK | |
| @@ -59,7 +61,7 @@ chpasswd - runner (list of "user:password"s from stdin) | |
| chpst - spawner | |
| chroot - spawner | |
| chrt - spawner | |
| - | chvt |
| + | chvt - leaks: get_console_fd_or_die() may open a new fd, or return one of stdio fds. Also, "rare" category. Can be noexec. |
| cksum - noexec. runner | |
| clear - NOFORK | |
| cmp - runner | |
| @@ -69,7 +71,7 @@ cp - noexec. runner | |
| cpio - runner | |
| crond - daemon | |
| crontab | |
| - | cryptpw |
| + | cryptpw - changes state: with --password-fd=N, moves N to stdin. Also, "rare" category. Can be noexec. |
| cttyhack - spawner | |
| cut - noexec. runner | |
| date - noexec. nofork candidate(needs to stop messing up env, free xasprintf result, not use xfuncs after xasprintf) | |