Differential D58189

mbuf: make m_unshare() allow unmapped mbufs
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Authored by takahiro.kurosawa_gmail.com on Jul 12 2026, 7:29 AM.

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Reviewers

gallatin

Group Reviewers

network

Commits

rGf2202ab5abda: mbuf: make m_unshare() allow unmapped mbufs

Summary

m_unshare() had crashed if unmapped mbufs exist in the mbuf chain.
This was because memcpy() with mtod() was used without making sure that
the mbuf was mapped. Use m_copydata() that cares unmapped mbufs instead.

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Repository

rG FreeBSD src repository

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Build Status

Buildable 74743
Build 71626: arc lint + arc unit

Event Timeline

takahiro.kurosawa_gmail.com created this revision.Jul 12 2026, 7:29 AM

Herald added subscribers: olce, glebius, imp. · View Herald TranscriptJul 12 2026, 7:29 AM

takahiro.kurosawa_gmail.com requested review of this revision.Jul 12 2026, 7:29 AM

Harbormaster completed remote builds in B74743: Diff 181821.Jul 12 2026, 7:29 AM

takahiro.kurosawa_gmail.com added a reviewer: network.Jul 12 2026, 7:30 AM

glebius added a reviewer: gallatin.Jul 12 2026, 4:54 PM

I'd write this as 'mcopydata(m,off, len, mtod(..));

Use m_copydata() instead of m_copyfromunmapped() as suggested by the review.

Harbormaster completed remote builds in B74795: Diff 181950.Jul 14 2026, 4:06 AM

takahiro.kurosawa_gmail.com edited the summary of this revision. (Show Details)Jul 14 2026, 4:08 AM

In D58189#1335203, @gallatin wrote:

I'd write this as 'mcopydata(m,off, len, mtod(..));

I've updated the code and the summary text according to your comment.
It gets much simpler. Thanks for the review!

gallatin accepted this revision.Jul 14 2026, 5:08 PM

This revision is now accepted and ready to land.Jul 14 2026, 5:08 PM

Closed by commit rGf2202ab5abda: mbuf: make m_unshare() allow unmapped mbufs (authored by takahiro.kurosawa_gmail.com, committed by kp). · Explain WhyJul 15 2026, 1:50 PM

This revision was automatically updated to reflect the committed changes.

kp added a commit: rGf2202ab5abda: mbuf: make m_unshare() allow unmapped mbufs.

Revision Contents
Changeset List

Path

Size

sys/

kern/

uipc_mbuf.c

21 lines

Diff 181821

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mbuf: make m_unshare() allow unmapped mbufsClosedPublicActions