[Vm-dev] Sorry, Sorry! [WAS: Trouble running OSVM in an Ubuntu 20/aarch64 docker]

Bruce O'Neel bruce.oneel at pckswarms.ch
Sat Jan 2 09:58:44 UTC 2021


Hi,  
  
The chmod should be  
  
chmod 1777 /dev/shm  
  
 ls -alh /dev/shm  


total 4.0K  


drwxrwxrwt  2 root root   60 Dez 21 12:06 .  


drwxr-xr-x 17 root root 5.6K Dez 21 12:06 ..  


-rw----rw-  1 root root 4.0K Dez 21 12:06 PHS-5723  


  
  
That 1 before the 777 sets the sticky bit.  
  
**RESTRICTED****DELETION****FLAG****OR****STICKY****BIT**  


       The  restricted  deletion  flag  or  sticky  bit is a single bit, whose  


       interpretation depends on the file type.  For directories, it  prevents  


       unprivileged  users  from  removing or renaming a file in the directory  


       unless they  own  the  file  or  the  directory;  this  is  called  the  


       restricted  deletion  flag  for the directory, and is commonly found on  


       world-writable directories like **/tmp**.  For regular files on some  older  


       systems,  the  bit saves the program's text image on the swap device so  


       it will load more quickly when run; this is called the stickybit.  


  
The sticky bit  plus 777 lets /tmp and /dev/shm work correctly by letting everyone create and delete files, but unless they are root only they can delete only their own files.  
  
It won't fail on a single user system if you just use 777, but, it is a security leak on a multi user system since it lets me manipulate your shared memory segments etc.  
cheers  
  
bruce  

> Hi Ken,  
>   
>  thanks for this!! I’ll try and add an error message to the failure to point users to the fix. This is another one like not being able to set the heartbeat thread priority that the vm needs to report as helpfully as possible.  
>   
>  _,,,^..^,,,_ (phone)  
>   
>  > On Dec 31, 2020, at 6:15 AM, Ken.Dickey at whidbey.com wrote:  
>  >  
>  > Apologies to all, I though I had trimmed the header on this..  
>  > -KenD  
>  > =============  
>  > Message: 6  
>  > Date: Thu, 31 Dec 2020 04:18:58 -0800  
>  > From: Christoph Thiede  
>  > To: OpenSmalltalk/opensmalltalk-vm  
>  >  
>  > Cc: Comment , OpenSmalltalk-Bot  
>  >  
>  > Subject: Re: [Vm-dev] [OpenSmalltalk/opensmalltalk-vm] Trouble running  
>  > OSVM in an Ubuntu 20/aarch64 docker (raspi) (#544)  
>  > Message-ID:  
>  >  
>  > Content-Type: text/plain; charset="utf-8"  
>  >  
>  > I have tried that and built the VM again, but I keep getting the same  
>  > mprotect error message :( Any other ideas?  
>  >  
>  > From: oscogvm/build.linux64ARMv8/HowToBuild:  
>  >  
>  > vvv======vvv  
>  >  
>  > If running the resultant squeak vm gives an error something like  
>  > mprotect(x,y,PROT_READ|PROT_EXEC)  
>  > or  
>  > memory_alias_map: shm_open: Permission denied  
>  > you need to enable shared memory for the COG JIT.  
>  >  
>  > As root:  
>  > chmod 777 /dev/shm  
>  > echo 'none /dev/shm tmpfs rw,nosuid,nodev 0 0' >> /etc/fstab  
>  > mount /dev/shm  
>  >  
>  > The squeak vm should now work.  
>  > ^^^======^^^
  

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