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Bug 1967686 - SIGINT not passed to scl based process when using sudo
Summary: SIGINT not passed to scl based process when using sudo
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: scl-utils
Version: 8.4
Hardware: Unspecified
OS: Unspecified
high
unspecified
Target Milestone: beta
: ---
Assignee: Michal Domonkos
QA Contact: Lukáš Zachar
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2021-06-03 15:32 UTC by Piyush Bhoot
Modified: 2022-05-10 14:53 UTC (History)
2 users (show)

Fixed In Version: scl-utils-2.0.2-15.el8
Doc Type: No Doc Update
Doc Text:
Clone Of:
Environment:
Last Closed: 2022-05-10 14:30:03 UTC
Type: Bug
Target Upstream Version:
Embargoed:


Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Knowledge Base (Solution) 6135671 0 None None None 2021-10-12 03:38:18 UTC
Red Hat Product Errata RHBA-2022:1959 0 None None None 2022-05-10 14:30:05 UTC

Description Piyush Bhoot 2021-06-03 15:32:49 UTC
Description of problem:

CTRL+C fails with error when command is invoked with sudo in scl environment.

Version-Release number of selected component (if applicable):
scl-utils-2.0.2-13.el8.x86_64

How reproducible:
Always when using sudo

Steps to Reproduce:
1.scl enable gcc-toolset-10 -- sudo tail -f /var/log/messages
2.ctrl+c


Actual results:
Jun  3 11:09:36  systemd[1]: Started /usr/bin/systemctl start man-db-
:
:
Jun  3 11:13:57  systemd[1]: Started Session 5 of user root.
^CProblem with executing command "/bin/bash /var/tmp/sclCpPZ9l"



Expected results:
Jun  3 11:09:36 vm252-219 systemd[1]: Started /usr/bin/systemctl start man-db-
:
:
Jun  3 11:13:57 vm252-219 systemd[1]: Started Session 5 of user root.
^C

Additional info:

Process stays on.

ps -ef | grep scl
root       54119   54082  0 11:06 pts/0    00:00:00 /usr/bin/scl enable gcc-toolset-10 bash
root       54120   54119  0 11:06 pts/0    00:00:00 /bin/bash /var/tmp/scluvOXF4
root       54163   54124  0 11:06 pts/0    00:00:00 grep --color=auto scl

 pstree -Aap 54119
scl,54119 enable gcc-toolset-10 bash
  `-bash,54120 /var/tmp/scluvOXF4
      `-bash,54124
          `-pstree,54483 -Aap 54119

- Issue seen only when using sudo for root and other users

1] Exits normally 
# scl enable gcc-toolset-10 bash
# tail -f /var/log/messages
Ctrl+C

2] Throws error

# scl enable gcc-toolset-10 bash
# sudo tail -f /var/log/messages
 Ctrl+C

3] strace
strace -ffo strace.out scl enable gcc-toolset-10 -- sudo tail -f /var/log/messages
:
:
openat(AT_FDCWD, "/var/tmp/sclaiLlVn", O_RDWR|O_CREAT|O_EXCL, 0600) = 3
fcntl(3, F_GETFL)                       = 0x8002 (flags O_RDWR|O_LARGEFILE)
fstat(3, {st_mode=S_IFREG|0600, st_size=0, ...}) = 0
write(3, "eval \"SCLS=( ${X_SCLS[*]} )\"\n 't"..., 62) = 62
close(3)                                = 0
rt_sigaction(SIGINT, {sa_handler=SIG_IGN, sa_mask=[], sa_flags=SA_RESTORER, sa_restorer=0x7f471aed8880}, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0
rt_sigaction(SIGQUIT, {sa_handler=SIG_IGN, sa_mask=[], sa_flags=SA_RESTORER, sa_restorer=0x7f471aed8880}, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
clone(child_stack=NULL, flags=CLONE_PARENT_SETTID|SIGCHLD, parent_tid=[54899]) = 54899
wait4(54899, 0x7ffd1515bbe8, 0, NULL)   = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGINT {si_signo=SIGINT, si_code=SI_KERNEL} ---
wait4(54899, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGINT}], 0, NULL) = 54899
rt_sigaction(SIGINT, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=SA_RESTORER, sa_restorer=0x7f471aed8880}, NULL, 8) = 0
rt_sigaction(SIGQUIT, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=SA_RESTORER, sa_restorer=0x7f471aed8880}, NULL, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_KILLED, si_pid=54899, si_uid=0, si_status=SIGINT, si_utime=0, si_stime=0} ---
write(2, "Problem with executing command \""..., 62) = 62

Comment 1 Michal Domonkos 2022-02-17 17:44:23 UTC
What happens here is that scl simply treats any abnormal process termination as an error and doesn't handle SIGINT in any special way.  The reason it "works" when using bash as the scl command and running tail in it (as described in Comment 0) is simply because scl is not involved there at all, and bash doesn't print an error on SIGINT.  
Normally, using sudo in the same scenario would behave the same way (no error), however this is a peculiarity of gcc-toolset-10 which ships a sudo wrapper (see Bug 849452 and a fixup Bug 1319936) that actually runs another scl instance nested - and scl, as mentioned above, prints an error on SIGINT.  So it's actually the nested scl instance that yields the error, not the parent one (but that's not important here.)

Anyway, handling SIGINT fixes all of the above, here's the patch:
https://github.com/sclorg/scl-utils/commit/9147d3b66e0a263c2eb427b7892b34c925363854

Comment 13 errata-xmlrpc 2022-05-10 14:30:03 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (scl-utils bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2022:1959


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