[SOLVED] weird permission denied error on compiled software

shivahoj · 12-31-2018, 05:34 PM

Hello all,
i have a small 4bay NAS system (ACER easystore H341, intel Atom 1,66 GHz), with a fresh Debian 9 installation.
There is a software https://github.com/merelin/mediasmartserverd, that drives the bay LEDs (activity and population of each bay). But when i compile it (as root), the binary gives permission denied, when executed. I remember having compiled this without problems some months ago, but i dont know what was different then (maybe debian 8?).
How do i inspect this software? I am no good in debuggers, disassembling etc.
Any hints or Tips? Any other information needed?

Dirk

This is the compile run:

Code:

root@nas:/root/mediasmartserverd-master# make
rm *.o mediasmartserverd core -f
g++ -Wall -O2 -o device_monitor.o -c src/device_monitor.cpp
g++ -Wall -O2 -o update_monitor.o -c src/update_monitor.cpp -pthread
g++ -Wall -O2 -o mediasmartserverd.o -c src/mediasmartserverd.cpp
g++ -Wall -O2 -o mediasmartserverd device_monitor.o update_monitor.o mediasmartserverd.o -ludev -ldl -lpthread

This is the contents of the directory after compiling:

Code:

root@nas:/root/mediasmartserverd-master# ls -la
total 344
drwx------  7 dirk users   4096 Dec 31 20:22 .
drwxrwsr-x 14 dirk users   4096 Dec 26 20:31 ..
-rw-r--r--  1 root root      47 Jan  7  2018 .gitignore
-rw-r--r--  1 root root     859 Jan  7  2018 LICENSE
-rw-r--r--  1 root root    1597 Jan  7  2018 Makefile
-rw-r--r--  1 root root    3399 Jan  7  2018 README.md
drwxr-xr-x  2 root root    4096 Jan  7  2018 bin
drwxr-xr-x  3 root root    4096 Jan  7  2018 debian
-rw-r--r--  1 root root   46568 Dec 31 20:22 device_monitor.o
drwxr-xr-x  3 root root    4096 Jan  7  2018 etc
drwxr-xr-x  3 root root    4096 Jan  7  2018 lib
-rwxr-xr-x  1 root root   98128 Dec 31 20:22 mediasmartserverd
-rw-r--r--  1 root root  116344 Dec 31 20:22 mediasmartserverd.o
-rw-r--r--  1 root root    3399 Jan  7  2018 readme.txt
drwxr-xr-x  2 root root    4096 Jan  7  2018 src
-rw-r--r--  1 root root   26544 Dec 31 20:22 update_monitor.o

This is the error message

Code:

root@nas:/root/mediasmartserverd-master# ./mediasmartserverd
-bash: ./mediasmartserverd: Permission denied

but as can be seen in the above directory listing, the file is executable, and root is the owner of it!
What linux knows about the file:

Code:

root@nas:/root/mediasmartserverd-master# file mediasmartserverd
mediasmartserverd: ELF 64-bit LSB shared object, x86-64, version 1 (GNU/Linux), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=891299afa7545d49dff9c313e9d2078dcc5bebcb, not stripped

Ztcoracat · 12-31-2018, 05:44 PM

Hi:

I was taught not to compile software as root.
The only time you need to become root is when it's time to run make install.

When you get a chance double check on the 'Install' or ReadMe file to see what's recommended to perform the installation.

Try using su - instead of sudo:-

berndbausch · 12-31-2018, 05:58 PM

For some reason, it turns out to be a “ELF 64-bit LSB shared object”. Shared objects can’t run. Try file /bin/ls to see the difference.

Why the compiler (or linker) did that to you, I can’t tell.

Ztcoracat · 12-31-2018, 06:00 PM

Quote:

Originally Posted by berndbausch

For some reason, it turns out to be a “ELF 64-bit LSB shared object”. Shared objects can’t run. Try file /bin/ls to see the difference.

Why the compiler (or linker) did that to you, I can’t tell.

Thanks for the info.

ehartman · 01-01-2019, 12:09 AM

Quote:

Originally Posted by Ztcoracat

Thanks for the info.

Essentially a "shared object" is a file, which is executed through a "real" executable (so it does have x rights, but is loaded for its functions, not executed sec). It doesn't have a main() part, only consists of functions that can be shared.
To enhance on the previous reply (#3):

Code:

$ ldd /bin/ls

will show which shared objects will be used BY the ls command.

Normally a shared object is given a .so or .so.<version> extension.

ehartman · 01-01-2019, 02:23 AM

Quote:

Originally Posted by ehartman

It doesn't have a main() part.

Later I thought: maybe that's the problem, that the make didn't link in the (compiled) source file with the main program routine, thus creating a shared object instead of an executable program.

Ztcoracat · 01-01-2019, 01:40 PM

Quote:

Originally Posted by ehartman

Later I thought: maybe that's the problem, that the make didn't link in the (compiled) source file with the main program routine, thus creating a shared object instead of an executable program.

I'm thinking that you are right because there have been many times when 'make' didn't work for me either:-

shivahoj · 02-23-2019, 06:56 AM

Hello, i finally found the solution:
i unzipped the source files as root, so the directory and all the files were owned by root.
unzipping the source files as a regular user lets me successfully compile the source, and run the binay