Fwd: Crashing the Linux System

Fwd: Crashing the Linux System

[LitHack]

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---------- Forwarded message ---------
From: LitHack <lithack0@gmail.com>
Date: Sat, 17 Jun 2023 at 08:52
Subject: Crashing the Linux System
To: <linux-kernel@vger.kernel.org>


Running the yes command in command substitution will crash the linux shell.
According to me inside command the substitution it is creating multiple
process(fork).  Command: `yes` or $(yes)

Here is the bug report:
Bug report <https://bugzilla.kernel.org/show_bug.cgi?id=217565>

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Re: Fwd: Crashing the Linux System

[Ellenor Bjornsdottir]

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Which shell? Zsh? Bash? There is no one Linux shell.

Le 17 juin 2023 03 h 38 min 28 s UTC, LitHack <lithack0@gmail.com> a écrit :
>---------- Forwarded message ---------
>From: LitHack <lithack0@gmail.com>
>Date: Sat, 17 Jun 2023 at 08:52
>Subject: Crashing the Linux System
>To: <linux-kernel@vger.kernel.org>
>
>
>Running the yes command in command substitution will crash the linux shell.
>According to me inside command the substitution it is creating multiple
>process(fork).  Command: `yes` or $(yes)
>
>Here is the bug report:
>Bug report <https://bugzilla.kernel.org/show_bug.cgi?id=217565>

-- 
Ellenor Bjornsdottir (she)
sysadmin umbrellix.net

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Re: Crashing the Linux System

[Bart Schaefer]

On Fri, Jun 16, 2023 at 8:38 PM LitHack <lithack0@gmail.com> wrote:
>
> Running the yes command in command substitution will crash the linux shell. According to me inside command the substitution it is creating multiple process(fork).  Command: `yes` or $(yes)

The "yes" command is defined to produce an unending stream of output.
The $(...) substitution is defined to capture all the output from a
command and substitute it as a string.  "All the output" of "yes" is
impossible to capture in finite memory.  The error I get from zsh is
the expected one:
zsh: fatal error: out of heap memory
There definitely are not multiple forks happening.

This is not a bug except in the sense that it was user error to use
$(yes) in the first place.  It's no different than deliberately
writing an infinite loop such as $(while true; do echo y; done).