syft does not find anything in archives if /tmp is a tmpfs

[martinetd]

What happened:

Running syft scan someimage.tar doesn't find anything on my system with /tmp mounted as tmpfs

What you expected to happen:

It should work as expected

Steps to reproduce the issue:

# if not already a tmpfs
sudo mount -t tmpfs tmpfs /tmp
# get any random archive
curl -O https://dl-cdn.alpinelinux.org/alpine/v3.20/releases/x86_64/alpine-minirootfs-3.20.0-x86_64.tar.gz
# run syft
syft alpine-minirootfs-3.20.0-x86_64.tar.gz
 ✔ Indexed file system                                          /tmp/syft-archive-contents-1080653417
 ✔ Cataloged contents                f7dc00a9fa83e70f0940486a37761faa850ed8d67ebc24a3fb6e93c832dca43d
   ├── ✔ Packages                        [0 packages]  
   └── ✔ Executables                     [0 executables]  
No packages discovered

Anything else we need to know?:

Patching the exclusion for tmpfs obviously works:

diff --git a/syft/internal/fileresolver/directory_indexer.go b/syft/internal/fileresolver/directory_indexer.go
index 92495ab77a36..bf0c1354303e 100644
--- a/syft/internal/fileresolver/directory_indexer.go
+++ b/syft/internal/fileresolver/directory_indexer.go
@@ -485,7 +485,7 @@ func keepUnixSystemMountPaths(infos []*mountinfo.Info) []string {
 		//     - tmpfs - used for /dev in special instances (within a container)
 
 		switch info.FSType {
-		case "proc", "procfs", "sysfs", "devfs", "devtmpfs", "udev", "tmpfs":
+		case "proc", "procfs", "sysfs", "devfs", "devtmpfs", "udev":
 			log.WithFields("mountpoint", info.Mountpoint).Debug("ignoring system mountpoint")
 
 			mountPaths = append(mountPaths, info.Mountpoint)

I guess these would make sense when running syft on a live container, but perhaps we should make sure we're not ignoring the filesystem that contains the scan target?
In the archive case, it's extracting the archive to /tmp/syft-archive-contents-foobar so I'd assume we get that /tmp path somewhere as "scan target", and that should always be allowed.
Anything below (e.g. if /tmp/syft-archive-contents-foobar/tmp) can be ignored as currently done.

Not sure how to do that properly so opening issue first; this can be worked around by running syft in a container so it doesn't see that /tmp is a tmpfs so there is no urgence.

Environment:

• Output of syft version: master
• OS (e.g: cat /etc/os-release or similar): linux

[martinetd]

Thanks!