LinuxQuestions.org - envar PATH when run by udev

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envar PATH when run by udev - poor choice?

Hello :)

The value of envar PATH for processes run by the udev system is "/usr/gnu/bin:/usr/local/bin:/bin:/usr/bin:.". If peer review (that's you!) agrees it is a poor choice how can I submit an enhancement request? The man pages do not say anything about bug reporting.

Here are reasons why it is a bizarre choice:

There is no /gnu/bin directory on as-installed Slackware.
/usr/local/bin is empty (or very nearly empty?) on as-installed Slackware.
Processes running under udev run as root; having "." in PATH is not good practice when running as root.
Processes running under udev are likely to be doing "system" work so executables from the sbin directories are likely to be used. For example, udevadm itself is /sbin/udevadm.

Presumably this PATH is set by udevd itself; it is not the PATH in effect when udevd is started by rc.M.

AFAIK udevd's PATH is not configurable.

The workaround is for processes initiated by udev to set a sane PATH for themselves, perhaps "/usr/sbin:/sbin:/usr/bin:/bin".

EDIT: seen on Slackware 13.0 32 bit.

EDIT2: rc.udev is run from rc.S, not rc.M as stated above :redface:

Best

Charles

Apparently older udevd cleaned PATH but not anymore (circumstantial). W/o need for patching, could starting Udev like 'env PATH=/usr/sbin:/sbin:/usr/bin:/bin /sbin/udevd --whatever-args' work? That is, if the "Steps to reproduce" method shows that helper apps inherit that path.

Quote:

Originally Posted by unSpawn (Post 3927730)

Apparently older udevd cleaned PATH but not anymore (circumstantial: ). W/o need for patching, could starting Udev like 'env PATH=/usr/sbin:/sbin:/usr/bin:/bin /sbin/udevd --whatever-args' work? That is, if the "Steps to reproduce" method shows that helper apps inherit that path.

Thanks unSpawn :) Have modified rc.udev and will report result after next reboot.

Further investigation confirms the initial impression that udev changes envar PATH, setting it to "/usr/gnu/bin:/usr/local/bin:/bin:/usr/bin:."

During execution of rc.udev, immediately before starting the udev daemon, $PATH is "/sbin:/bin".
The command used to start the udev daemon was modified to

Code:

env PATH=/usr/sbin:/sbin:/usr/bin:/bin/sbin/ udevd --daemon
A script called via a udev rule was modified to log $PATH and showed "/usr/gnu/bin:/usr/local/bin:/bin:/usr/bin:."

Looking deeper, trying to find out where this PATH is set:

Code:

root@CW8:~# strings /sbin/udevd | grep sbin

root@CW8:~# file /sbin/udevd

/sbin/udevd: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), stripped

root@CW8:~# ldd /sbin/udevd

        linux-gate.so.1 =>  (0xffffe000)

        libc.so.6 => /lib/libc.so.6 (0xb7eb3000)

        /lib/ld-linux.so.2 (0xb802d000)

And there I got stuck.

Perhaps an strace would reveal something.

Quote:

Originally Posted by mRgOBLIN (Post 3928241)

Perhaps an strace would reveal something.

Thanks mRgOBLIN :)

I tried that but the strace output stopped before a device could be plugged in. strace showed reading many udev rules and ended with

Code:

clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7d9c708) = 6604

munmap(0xb7d2d000, 163840)              = 0

close(4)                                = 0

close(5)                                = 0

exit_group(0)                          = ?

I guess it "exec"ed a new process and the new process was not "strac"ed ???

Unless there are any further suggestions on how to investigate this so I can make a more useful request, how can I submit an enhancement request?

Further investigation shows that the $PATH is bash' default so presumably udevd is not setting a PATH environment variable

Code:

c@CW8:~$ unset PATH

c@CW8:~$ /bin/bash

c@CW8:~$ echo $PATH

/usr/gnu/bin:/usr/local/bin:/bin:/usr/bin:.

Quote:

Originally Posted by catkin (Post 3928294)

... how can I submit an enhancement request?

I sent an email to info <antelope> AT <fish> slackware.com asking them to consider modifying udevd to set a PATH or bash to have a default PATH that is useful on Slackware.