[BusyBox 0004054]: busybox 1.9.1 killall command doesn't work

bugs at busybox.net bugs at busybox.net
Mon Jul 14 01:17:04 UTC 2008


A NOTE has been added to this issue. 
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http://busybox.net/bugs/view.php?id=4054 
====================================================================== 
Reported By:                bwondu
Assigned To:                BusyBox
====================================================================== 
Project:                    BusyBox
Issue ID:                   4054
Category:                   Other
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     assigned
====================================================================== 
Date Submitted:             07-10-2008 15:41 PDT
Last Modified:              07-13-2008 18:17 PDT
====================================================================== 
Summary:                    busybox 1.9.1 killall command doesn't work
Description: 
executing killall <processname> retrun killall: <processname>: no process
killed

I tried to do the same thing as in busybox 1.1.0 which is in
libbb/procps.c (read_to_buf() function) replace any character < ' ' in the
string read from /proc/%d/cmdline.  In libbb/find_pid_by_name.c
(find_pid_by_name() function), I removed the call to bb_basename and did a
strstr instead of strcmp and it worked.  But since there are other
dependencies to these functions, I want to make sure that this doesn't
break anything.  If you have a better fix for it please let me know as
killall in Busybox 1.1.0 works perfectly fine. Thanks
====================================================================== 

---------------------------------------------------------------------- 
 vda - 07-10-08 16:41  
---------------------------------------------------------------------- 
Before trying to fix it, we need to understand how exactly it fails.

Does it happen with 1.11.0? For me it works:

# strace -o log killall top

# tail log
read(5, "32314 (mc) S 32312 32314 32312 3"..., 1023) = 244
close(5)                                = 0
open("/proc/32314/cmdline", O_RDONLY|O_LARGEFILE) = 5
read(5, "/usr/bin/mc\0-d\0", 1023)      = 15
close(5)                                = 0
getdents64(3, /* 0 entries */, 1024)    = 0
close(3)                                = 0
kill(707, SIGTERM)                      = 0
kill(14022, SIGTERM)                    = 0
_exit(0)                                = ?

Can you provide your example? Attach full strace log to this bug. 

---------------------------------------------------------------------- 
 bwondu - 07-10-08 21:00  
---------------------------------------------------------------------- 
open("/proc/25936/cmdline", O_RDONLY|O_LARGEFILE) = 4
read(4, "./busybox\0killall\0top\0", 1023) = 22
close(4)                                = 0
getdents64(3, /* 0 entries */, 1024)    = 0
close(3)                                = 0
brk(0x8aad000)                          = 0x8aad000
ioctl(2147483647, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbfe39758) = -1 EBADF
(Bad file descriptor)
brk(0x8aae000)                          = 0x8aae000
write(2, "killall: top: no process killed\n", 32) = 32
_exit(1)                                = ? 

---------------------------------------------------------------------- 
 vda - 07-11-08 03:08  
---------------------------------------------------------------------- 
This is not a full strace log. Instead of pasting "tail log" result, push
[Upload File] button on this web page and upload _entire_ strace log file.
Please also specify the name of process you are trying to kill - "killall
<WHICH_PROGRAM?>". 

---------------------------------------------------------------------- 
 bwondu - 07-11-08 03:37  
---------------------------------------------------------------------- 
I have uploaded a full tracelog.  Please refer to stracelog.  I tried to
kill nonsenseprocess.sh 

---------------------------------------------------------------------- 
 vda - 07-11-08 03:59  
---------------------------------------------------------------------- 
Here is it:

open("/proc/32635/stat", O_RDONLY|O_LARGEFILE) = 4
read(4, "32635 (nonsenseprocess) S 32604 "..., 1023) = 200
close(4)                                = 0

The _ONLY_ way to match scripts by name in Linux is to look at so called
comm field in /proc/$PID/stat.

Because /proc/$PID/cmdline will have "/bin/sh",NUL,"<scriptname>",NUL,...
and /proc/$PID/exe symlink will point to /bin/sh, and neither of these are
indicative that this process is named <scriptname>, right?

So we are left with /proc/$PID/stat's comm field - the
"...(<scriptname>)..." thing. But it is limited to 15 chars. If killall
sees comm field which is exactly 15 chars long, it does not use it because
it is truncated - in your example, it can be a truncated version of
"nonsenseprocess.sh" or truncated version of
"nonsenseprocess_which_you_dont_want_to_kill_at_all_costs"!

Killall should be able to kill scripts with names less than 15 chars. 

---------------------------------------------------------------------- 
 bwondu - 07-13-08 18:17  
---------------------------------------------------------------------- 
Since we know how many bytes were read from the /proc/%d/cmd file, we can
change the null characters to non-null values (spaces).  If you use that
file, there is no need to worry about truncation.

My 2 cents. 

Issue History 
Date Modified   Username       Field                    Change               
====================================================================== 
07-10-08 15:41  bwondu         New Issue                                    
07-10-08 15:41  bwondu         Status                   new => assigned     
07-10-08 15:41  bwondu         Assigned To               => BusyBox         
07-10-08 16:41  vda            Note Added: 0009134                          
07-10-08 21:00  bwondu         Note Added: 0009144                          
07-10-08 21:01  bwondu         File Added: log                              
07-11-08 02:39  bwondu         File Added: stracelog                        
07-11-08 03:08  vda            Note Added: 0009154                          
07-11-08 03:37  bwondu         Note Added: 0009164                          
07-11-08 03:59  vda            Note Added: 0009174                          
07-13-08 18:17  bwondu         Note Added: 0009234                          
======================================================================




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