On 5/8/25 10:12 PM, Mitchell Dorrell wrote:
> This is not a bug report and I'm not really seeking assistance, I'm just
> inviting discussion because... this shouldn't be able to happen, right?
>
> Earlier today, I opened a terminal using urxvt, then initiated an SSH
> connection to a remote machine. On the remote machine, I ran a command
> roughly like this (but as a one-liner):
>
> for d in path1 path2 path3; do
> files=$(find $d -not -type d -exec readlink -f {} \; | sort -u);
> for f in $files; do
> cat $f | tr ' ' '\n' | pipe_through_sed_and_grep_etc;
> done;
> done
>
> ... which caused grep to mention finding some matches inside binary data
> via stdin. After (insufficiently) adding to the pipeline to filter the
> output down to just the matching strings, I added '-a' to the grep
> commands, hit enter, briefly saw some junk printed to the terminal, and
> then my screen went black and I noticed that my power LED was dark.
>
> There are 468 null bytes in /var/log/messages at the crash time.
>
> Neither urxvt, nor bash, nor ssh were running as root, and I'm pretty
> sure I had rebooted since my last @world update, so there shouldn't be
> any outdated libraries in play.
>
> Userspace applications shouldn't be able to crash the system, right?I would say that this is an almost fallacious way to look at things, honestly. urxvt is a userspace application, so it "can't" crash the system, no matter what I do with it... right? Even if I run `sudo /usr/sbin/crashsystem`, it's running in a userspace application, what can it do really? Userspace applications have to make use of kernel facilities for everything they do, such as displaying graphics on the screen. A not-entirely-uncommon cause of system crashes is bugs being triggered in a GPU driver. That's deeply trusted code running at a higher permission level than merely sudo. Of course, it "should" be designed to not mishandle bad data, and for the most part, they do a good job at that. But things happen. It's a valid possibility. :) -- Eli Schwartz
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