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Differential D58317

unix: Preserve FD_RESOLVE_BENEATH when passing an fd
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Authored by markj on Jul 17 2026, 9:51 PM.

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rG30758138f2e3: unix: Preserve FD_RESOLVE_BENEATH when passing an fd
rG441885dcfff3: unix: Preserve FD_RESOLVE_BENEATH when passing an fd
rG586e2b3d89d6: unix: Preserve FD_RESOLVE_BENEATH when passing an fd

Summary

The FD_RESOLVE_BENEATH flag is supposed to be sticky. It's set when you
receive an fd from a different jail and preserved by openat(<dfd>) etc..
However, if you send the fd to yourself, the flag is stripped since
SCM_RIGHTS message don't preserve file descriptor flags.

Fix this by preserving those flags and checking for UF_RESOLVE_BENEATH
in restrict_rights().

Fixes: 350ba9672a7f ("unix: Set O_RESOLVE_BENEATH on fds transferred between jails")

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rG FreeBSD src repository

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Event Timeline

markj created this revision.Jul 17 2026, 9:51 PM

Herald added subscribers: olce, glebius, imp. · View Herald TranscriptJul 17 2026, 9:51 PM

markj requested review of this revision.Jul 17 2026, 9:51 PM

Harbormaster completed remote builds in B74905: Diff 182163.Jul 17 2026, 9:51 PM

kib accepted this revision.Jul 17 2026, 11:01 PM

kib added inline comments.

sys/kern/uipc_usrreq.c
3521–3525	BTW why not return the UF_ flag(s) directly from restrict_rights, instead of using ternary operator in the calling place?

This revision is now accepted and ready to land.Jul 17 2026, 11:01 PM

Apply kib's suggestion

This revision now requires review to proceed.Jul 22 2026, 3:45 PM

Harbormaster completed remote builds in B75015: Diff 182466.Jul 22 2026, 3:45 PM

kib accepted this revision.Jul 22 2026, 9:04 PM

kib added inline comments.

sys/kern/uipc_usrreq.c
3524	`else` is not needed.

This revision is now accepted and ready to land.Jul 22 2026, 9:04 PM

Closed by commit rG586e2b3d89d6: unix: Preserve FD_RESOLVE_BENEATH when passing an fd (authored by markj). · Explain WhyJul 24 2026, 9:07 PM

This revision was automatically updated to reflect the committed changes.

markj added a commit: rG586e2b3d89d6: unix: Preserve FD_RESOLVE_BENEATH when passing an fd.

markj added a commit: rG441885dcfff3: unix: Preserve FD_RESOLVE_BENEATH when passing an fd.Wed, Aug 5, 3:16 PM

markj added a commit: rG30758138f2e3: unix: Preserve FD_RESOLVE_BENEATH when passing an fd.Thu, Aug 6, 3:02 PM

Revision Contents
Changeset List

Path

Size

sys/

kern/

27 lines

tests/

sys/

kern/

unix_passfd_test.c

31 lines

Diff 182636

sys/kern/uipc_usrreq.c

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tests/sys/kern/unix_passfd_test.c

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