msdosfs: replace '/' in direntries with '?'
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Authored by kib on Jul 17 2025, 1:14 AM.

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markj
emaste

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rG29af6d2e2ec9: msdosfs: replace '/' in direntries with '?'

Summary

PR:     288266
Reported by:    Robert Morris <rtm@lcs.mit.edu>

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rG FreeBSD src repository

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kib created this revision.Jul 17 2025, 1:14 AM

Herald added a subscriber: imp. · View Herald TranscriptJul 17 2025, 1:14 AM

kib requested review of this revision.Jul 17 2025, 1:14 AM

Might be it even makes sense to remount ro, but the damage is still there so probably not a big deal.
I do not think that we must filter out such entries, only return them into the safe territory.

Isn't this a more general problem? e.g. UFS also does not validate the returned directory entries.

sys/fs/msdosfs/msdosfs_conv.c
817	IMO it is a bit clearer if the substitution is done in dos2unixfn().

In D51365#1173189, @markj wrote:

Isn't this a more general problem? e.g. UFS also does not validate the returned directory entries.

I do not think so. For UFS (and probably ZFS) it would be a different issue:

for UFS we trust on-disc format, and the issue like invalid dirent must be fixed by fsck.
for msdosfs, the volume content is more often cannot be relied upon, it is either comes from other OS, or is even dynamically generated. In modern times msdosfs volume is typically the systems communication and interoperability mechanism.

So we must be prepared for invalid msdosfs formats, while we consider UFS format errors as exceptions.

kib added inline comments.Jul 17 2025, 9:33 PM