** Description changed:
An SSH terminal into an Ubuntu server (tested on 18.04.5) hangs running
a command using 'sudo' when 'use_pty' is set in /etc/sudoers.
Steps to reproduce ('sudo' version --> 1.8.21p2-3ubuntu1.2):
1) Log in into an Ubuntu server (tested on 18.04.5 using SSH)
2) Ensure that /etc/sudoers has the following line (add this line if not
present)
Defaults use_pty
- 3) Execute the following:
+ 3) Execute the following (test 'sudo' command):
for i in {1..10}; do sudo -- cat /var/log/syslog; done
The terminal hangs and the following backtrace is obtained:
(gdb) bt
#0 0x00007f751d5c8cc4 in __GI___poll (fds=0x55d0159917b0, nfds=1,
timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:29
#1 0x00007f751d8b146a in poll (__timeout=<optimized out>, __nfds=<optimized
out>, __fds=<optimized out>) at /usr/include/x86_64-linux-gnu/bits/poll2.h:46
#2 sudo_ev_scan_impl (base=base@entry=0x55d015990dc0, flags=flags@entry=0)
at ../../../lib/util/event_poll.c:155
#3 0x00007f751d8aa74d in sudo_ev_loop_v1 (base=base@entry=0x55d015990dc0,
flags=flags@entry=0) at ../../../lib/util/event.c:617
#4 0x000055d01570597a in del_io_events (nonblocking=nonblocking@entry=false)
at ../../src/exec_pty.c:1537
#5 0x000055d015707b97 in pty_close (cstat=0x7ffd074d6110) at
../../src/exec_pty.c:697
#6 exec_pty (details=details@entry=0x55d01591e0e0 <command_details>,
cstat=cstat@entry=0x7ffd074d6110) at ../../src/exec_pty.c:1412
#7 0x000055d015701178 in sudo_execute (details=0x55d01591e0e0
<command_details>, cstat=0x7ffd074d6110) at ../../src/exec.c:391
#8 0x000055d01570e15b in run_command (details=0x55d01591e0e0
<command_details>) at ../../src/sudo.c:968
#9 0x000055d0156ff9a0 in main (argc=<optimized out>, argv=<optimized out>,
envp=<optimized out>) at ../../src/sudo.c:294
A similar (most likely the same) bug has been reported here
https://access.redhat.com/solutions/3404401.
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https://bugs.launchpad.net/bugs/1895757
Title:
Terminal hangs running sudo when "use_pty" is set in /etc/sudoers
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