Re: [syzbot] [ext4?] kernel panic: EXT4-fs (device loop0): panic forced after error (3)

Theodore Ts'o
2023-08-17T16:11:27Z

On Thu, Aug 17, 2023 at 09:47:48AM -0500, Eric Sandeen wrote:
>
> Just to play devil's advocate here - (sorry) - I don't see this as any
> different from any other "malicious" filesystem image.
>
> I've never been a fan of the idea that malicious images are real security
> threats, but whether the parking lot USB stick paniced the box in an
> unexpected way or "on purpose," the result is the same ...
>
> I wonder if it might make sense to put EXT4_MOUNT_ERRORS_PANIC under a
> sysctl or something, so that admins can enable it only when needed.

Well, if someone is stupid enough to plug in a parking lot USB stick
into their system, they get everything they deserve. And a forced
panic isn't going to lead a more privilege escalation attack, so I
really don't see a problem if a file system which is marked "panic on
error", well, causes a panic. It's a good way of (harmlessly)
punishing stupid user tricks. :-)

The other way of thinking about it is that if your threat model
includes an attacker with physical access to the server with a USB
port, attacks include a cable which has a USB port on one side, and a
120V/240V AC mains plug on the the other. This will very likely cause
a system shutdown, even if they don't have automount enabled. :-)

- Ted