[Bug 1317136] Re: useful Yama EPERM error message missing (regression)

[Marc Deslauriers]

** Description changed:

- Trusty's gdb and ltrace have lost the helpful error details when ptrace
- attach fails. Compare to strace:
+ SRU:
+ 
+ [Impact]
+ ltrace and gdb users may be stumped by the ptrace restrictions that are enabled by default in Ubuntu. Unfortunately, the patches that print a detailed informative error message in previous Ubuntu releases no longer work or haven't been applied in Trusty.
+ 
+ [Test Case]
+ 
+ $ ltrace -p 1 should display the following:
+ Cannot attach to pid 1: 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
+ 
+ $ gdb -p 1 should display a similar error message
+ 
+ [Regression Potential]
+ This patch is in the error condition, so regression is unlikely. Worst case, it could prevent ltrace or gdb from working at all.
+ 
+ 
+ 
+ Original description:
+ Trusty's gdb and ltrace have lost the helpful error details when ptrace attach fails. Compare to strace:
  
  $ strace -p 1
  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
  
  $ gdb -p 1
  GNU gdb (Ubuntu 7.7-0ubuntu3) 7.7
  ...
  Attaching to process 1
  ptrace: Operation not permitted.
  
  $ ltrace -p 1
  Cannot attach to pid 1: Operation not permitted
  
- 
- In Precise ltrace has the correct error (though gdb is still missing it -- this was lost quite some time ago it seems):
+ In Precise ltrace has the correct error (though gdb is still missing it
+ -- this was lost quite some time ago it seems):
  
  $ ltrace -p 1
  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
  Cannot attach to pid 1: Operation not permitted

** Changed in: gdb (Ubuntu Trusty)
       Status: Confirmed => In Progress

** Changed in: ltrace (Ubuntu Trusty)
       Status: Confirmed => In Progress

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https://bugs.launchpad.net/bugs/1317136

Title:
  useful Yama EPERM error message missing (regression)

Status in “gdb” package in Ubuntu:
  Fix Released
Status in “ltrace” package in Ubuntu:
  Fix Released
Status in “gdb” source package in Trusty:
  In Progress
Status in “ltrace” source package in Trusty:
  In Progress
Status in “gdb” source package in Utopic:
  Fix Released
Status in “ltrace” source package in Utopic:
  Fix Released

Bug description:
  SRU:

  [Impact]
  ltrace and gdb users may be stumped by the ptrace restrictions that are enabled by default in Ubuntu. Unfortunately, the patches that print a detailed informative error message in previous Ubuntu releases no longer work or haven't been applied in Trusty.

  [Test Case]

  $ ltrace -p 1 should display the following:
  Cannot attach to pid 1: 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

  $ gdb -p 1 should display a similar error message

  [Regression Potential]
  This patch is in the error condition, so regression is unlikely. Worst case, it could prevent ltrace or gdb from working at all.


  
  Original description:
  Trusty's gdb and ltrace have lost the helpful error details when ptrace attach fails. Compare to strace:

  $ strace -p 1
  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

  $ gdb -p 1
  GNU gdb (Ubuntu 7.7-0ubuntu3) 7.7
  ...
  Attaching to process 1
  ptrace: Operation not permitted.

  $ ltrace -p 1
  Cannot attach to pid 1: Operation not permitted

  In Precise ltrace has the correct error (though gdb is still missing
  it -- this was lost quite some time ago it seems):

  $ ltrace -p 1
  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
  Cannot attach to pid 1: Operation not permitted

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