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[Bug 1495706] [NEW] strace cannot attach to process despite being root and setting scope

To: kernel-packages@xxxxxxxxxxxxxxxxxxx
From: Mario Vietri <1495706@xxxxxxxxxxxxxxxxxx>
Date: Mon, 14 Sep 2015 22:08:15 -0000
Reply-to: Bug 1495706 <1495706@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx
Public bug reported:

I am trying to run `strace` against kworker, but I cannot attach strace
despite havingset ptrace_scope=0 and being root.

Here is the proof:

# echo 1 >  /proc/sys/kernel/yama/ptrace_scope     
root@rasal:/home/me# whoami
root
root@rasal:/home/me# cat /proc/sys/kernel/yama/ptrace_scope 
0
root@rasal:/home/me# ps ax | grep kworker
    5 ?        S<     0:00 [kworker/0:0H]
   31 ?        S<     0:00 [kworker/1:0H]
   35 ?        S      0:00 [kworker/2:0]
   36 ?        S<     0:00 [kworker/2:0H]
   41 ?        S<     0:00 [kworker/3:0H]
   58 ?        S      0:00 [kworker/1:1]
   76 ?        S      0:00 [kworker/3:1]
   78 ?        S      0:00 [kworker/1:2]
   79 ?        S      0:00 [kworker/2:1]
  149 ?        S      0:00 [kworker/0:1]
  162 ?        S      0:00 [kworker/u16:3]
  163 ?        S      0:00 [kworker/u16:4]
  164 ?        S      0:00 [kworker/u16:5]
  448 ?        S<     0:00 [kworker/3:1H]
  449 ?        S<     0:00 [kworker/1:1H]
  451 ?        S<     0:00 [kworker/2:1H]
  452 ?        S<     0:00 [kworker/0:1H]
  560 ?        S      0:00 [kworker/3:2]
  604 ?        S      0:00 [kworker/0:2]
 1006 ?        S<     0:00 [kworker/u17:0]
 1017 ?        S<     0:00 [kworker/u17:1]
 4222 ?        S      0:00 [kworker/3:0]
 4249 pts/4    S+     0:00 grep --color=auto kworker
root@rasal:/home/me# strace -p 4222
strace: attach: ptrace(PTRACE_ATTACH, ...): Operation not permitted
Could not attach to process.  If your uid matches the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user.  For more details, see /etc/sysctl.d/10-ptrace.conf
root@rasal:/home/me#  uname -a
Linux rasal 3.16.0-49-generic #65~14.04.1-Ubuntu SMP Wed Sep 9 10:03:23 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux        

Any info on this?

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-3.16.0-49-generic 3.16.0-49.65~14.04.1
ProcVersionSignature: Ubuntu 3.16.0-49.65~14.04.1-generic 3.16.7-ckt15
Uname: Linux 3.16.0-49-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.13
Architecture: amd64
CurrentDesktop: KDE
Date: Tue Sep 15 00:01:12 2015
InstallationDate: Installed on 2014-05-05 (497 days ago)
InstallationMedia: Kubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.1)
SourcePackage: linux-lts-utopic
UpgradeStatus: Upgraded to trusty on 2014-11-21 (297 days ago)

** Affects: linux-lts-utopic (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug trusty

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https://bugs.launchpad.net/bugs/1495706

Title:
  strace cannot attach to process despite being root and setting scope

Status in linux-lts-utopic package in Ubuntu:
  New

Bug description:
  I am trying to run `strace` against kworker, but I cannot attach
  strace despite havingset ptrace_scope=0 and being root.

  Here is the proof:

  # echo 1 >  /proc/sys/kernel/yama/ptrace_scope     
  root@rasal:/home/me# whoami
  root
  root@rasal:/home/me# cat /proc/sys/kernel/yama/ptrace_scope 
  0
  root@rasal:/home/me# ps ax | grep kworker
      5 ?        S<     0:00 [kworker/0:0H]
     31 ?        S<     0:00 [kworker/1:0H]
     35 ?        S      0:00 [kworker/2:0]
     36 ?        S<     0:00 [kworker/2:0H]
     41 ?        S<     0:00 [kworker/3:0H]
     58 ?        S      0:00 [kworker/1:1]
     76 ?        S      0:00 [kworker/3:1]
     78 ?        S      0:00 [kworker/1:2]
     79 ?        S      0:00 [kworker/2:1]
    149 ?        S      0:00 [kworker/0:1]
    162 ?        S      0:00 [kworker/u16:3]
    163 ?        S      0:00 [kworker/u16:4]
    164 ?        S      0:00 [kworker/u16:5]
    448 ?        S<     0:00 [kworker/3:1H]
    449 ?        S<     0:00 [kworker/1:1H]
    451 ?        S<     0:00 [kworker/2:1H]
    452 ?        S<     0:00 [kworker/0:1H]
    560 ?        S      0:00 [kworker/3:2]
    604 ?        S      0:00 [kworker/0:2]
   1006 ?        S<     0:00 [kworker/u17:0]
   1017 ?        S<     0:00 [kworker/u17:1]
   4222 ?        S      0:00 [kworker/3:0]
   4249 pts/4    S+     0:00 grep --color=auto kworker
  root@rasal:/home/me# strace -p 4222
  strace: attach: ptrace(PTRACE_ATTACH, ...): Operation not permitted
  Could not attach to process.  If your uid matches the uid of the target
  process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
  again as the root user.  For more details, see /etc/sysctl.d/10-ptrace.conf
  root@rasal:/home/me#  uname -a
  Linux rasal 3.16.0-49-generic #65~14.04.1-Ubuntu SMP Wed Sep 9 10:03:23 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux        

  Any info on this?

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-3.16.0-49-generic 3.16.0-49.65~14.04.1
  ProcVersionSignature: Ubuntu 3.16.0-49.65~14.04.1-generic 3.16.7-ckt15
  Uname: Linux 3.16.0-49-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.13
  Architecture: amd64
  CurrentDesktop: KDE
  Date: Tue Sep 15 00:01:12 2015
  InstallationDate: Installed on 2014-05-05 (497 days ago)
  InstallationMedia: Kubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.1)
  SourcePackage: linux-lts-utopic
  UpgradeStatus: Upgraded to trusty on 2014-11-21 (297 days ago)

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Follow ups

[Bug 1495706] Re: strace cannot attach to process despite being root and setting scope
From: Mario Vietri, 2015-09-14