pgrep reports error "cannot allocate" when run without stack limit

Bug #1874824 reported by Sven Hartrumpf on 2020-04-24
This bug affects 8 people
Affects Status Importance Assigned to Milestone
procps (Debian)
procps (Ubuntu)
Status tracked in Hirsute

Bug Description

If you have no stack limit (ulimit -S -s unlimited), any pgrep call will fail with an error:

> pgrep vim
pgrep: cannot allocate 4611686018427387903 bytes

If you have a high stack limit (e.g. ulimit -S -s 500000), pgrep is very slow:

> time pgrep vim
real 8.48s user 8.40s syst 0.07s busy 99% rmem 253444

The relevant upstream bug report could be:
Archlinux bug report:

  Installed: 2:3.3.16-1ubuntu2
  500 focal/main amd64 Packages

Sven Hartrumpf (hartrumpf) wrote :

For the unlimited case, there is also Debian bug #955697
Those bug reports do not mention the massive slowdown linear in stack limit.

Sven Hartrumpf (hartrumpf) wrote :

The problem is the same for other popular tools like pkill from the same package.

Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in procps (Ubuntu):
status: New → Confirmed
Sven Hartrumpf (hartrumpf) wrote :

Archlinux fixed this bug today, now in testing stage. Any news for Ubuntu?

Sven Hartrumpf (hartrumpf) wrote :

I installed procps-ng myself on all our Ubuntu 20.04 computers. This fixed both problems, slow pgrep / pkill and crashing pgrep / pkill.

Changed in procps (Debian):
status: Unknown → New
Sven Hartrumpf (hartrumpf) wrote :

The Arch Linux fix appeared in Manjaro. I can confirm that it works on Manjaro machines.

Sven Hartrumpf (hartrumpf) wrote :

Even worse for Ubuntu 20.10 (procps 2:3.3.16-5ubuntu2). With a stack limit of 500000, almost 11 seconds for a simple pgrep; without stacklimit, immediate crash.

Hassan El Jacifi (waver) on 2020-11-11
tags: added: groovy
Vasilis (vasilis-vlachoudis) wrote :

It appeared today, after rebooting with the latest kernel, however I have not updated procps since some time now and it was working before

Sven Hartrumpf (hartrumpf) wrote :

Can the bug fix be applied for Ubuntu 21.04? Please.

On slow machines like a Raspberry 4 with stack limit 500000 (Ubuntu 20.10), a single pgrep call takes 17 seconds!

tags: added: hirsute
Robie Basak (racb) wrote :
tags: added: bitesize patch rls-hh-incoming
Changed in procps (Ubuntu):
status: Confirmed → Triaged
tags: added: fr-1174
tags: removed: rls-hh-incoming
Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in procps (Ubuntu Focal):
status: New → Confirmed
Changed in procps (Ubuntu Groovy):
status: New → Confirmed
Luke Yeager (luke-yeager) wrote :

FWIW, I was able to apply bb96fc4295 cleanly to the current 20.04 package (2:3.3.16-1ubuntu2) and it works for me.

apt-get -y source procps && cd procps-*
curl -fSsL -o debian/patches/sc_arg_max
echo sc_arg_max >>debian/patches/series
dch --local myorg 'Apply patch: "pgrep: check sanity of SC_ARG_MAX"'
debuild -us -uc -G -i -tc

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