Public bug reported:
The call to ptrace(PTRACE_TRACEME) fails in gdbserver in spite of
ptrace_scope being 0. As a result gdbserver hangs and is impossible to
use. When run with sudo it works fine. This seems to be a kernel bug.
# which gdbserver
/usr/bin/gdbserver
# cat /proc/sys/kernel/yama/ptrace_scope
0
# gdbserver :9091 /bin/true
<no output>
# sudo gdbserver :9091 /bin/true
Process /bin/true created; pid = 31071
Listening on port 9091
# strace -f gdbserver :9091 /bin/true
...
ptrace(PTRACE_TRACEME) = -1 EPERM (Operation not permitted)
...
# getcap /usr/bin/gdbserver
<no output>
Adding "setcap cap_sys_ptrace=+eip" to gdbserver doesn't change
anything.
Further details:
# lsb_release -rd
Description: Ubuntu 18.04.5 LTS
Release: 18.04
# apt-cache policy linux-generic
linux-generic:
Installed: 4.15.0.118.105
Candidate: 4.15.0.118.105
Version table:
*** 4.15.0.118.105 500
500 http://aptrepo/ubuntu bionic-updates/main amd64 Packages
500 http://aptrepo/ubuntu bionic-security/main amd64 Packages
100 /var/lib/dpkg/status
4.15.0.20.23 500
500 http://aptrepo/ubuntu bionic/main amd64 Package
** Affects: gdb (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1897187
Title:
Unable to ptrace(PTRACE_TRACEME) without sudo
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