vfs: Avoid a comparison with an uninitialized field in setutimes()
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Authored by markj on Aug 8 2021, 9:53 PM.

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rGeca9ac5a32e4: vfs: Avoid a comparison with an uninitialized field in setutimes()

Summary

Some filesystems, e.g., devfs, do not populate va_birthtime in their
GETATTR implementations. To handle this, make sure that va_birthtime is
initialized to the quasi-standard value of { VNOVAL, 0 } before calling
VOP_GETATTR.

Reported by: KMSAN
Sponsored by: The FreeBSD Foundation

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rG FreeBSD src repository

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markj created this revision.Aug 8 2021, 9:53 PM

Herald added a subscriber: imp. · View Herald TranscriptAug 8 2021, 9:53 PM

markj requested review of this revision.Aug 8 2021, 9:53 PM

Harbormaster completed remote builds in B40931: Diff 93423.Aug 8 2021, 9:53 PM

I am fine with this, but also wonder if it makes sense to fill birthtime for devfs. We can record the make_dev() time in cdev_priv inside devfs_alloc()

This revision is now accepted and ready to land.Aug 8 2021, 10:24 PM

To be clear, this change is mimicking vop_stdstat(), which pre-initializes several fields explicitly.

In D31468#709284, @kib wrote:

I am fine with this, but also wonder if it makes sense to fill birthtime for devfs. We can record the make_dev() time in cdev_priv inside devfs_alloc()

I can't see any problem with that, but I am not sure whether it would be useful to anyone vs. simply initializing va_birthtime to {-1, 0} in devfs_getattr().

Closed by commit rGeca9ac5a32e4: vfs: Avoid a comparison with an uninitialized field in setutimes() (authored by markj). · Explain WhyAug 9 2021, 5:49 PM

This revision was automatically updated to reflect the committed changes.

markj added a commit: rGeca9ac5a32e4: vfs: Avoid a comparison with an uninitialized field in setutimes().