auth: Honor file capabilities under no_new_privs - #14912
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Ambient capability support made execve ignore file capabilities when
no_new_privs is set. Linux does not do this. It skips setuid/setgid
bits under no_new_privs, but still applies file capabilities and only
stops them from adding to the permitted set. So capabilities the task
already holds are kept, and ambient capabilities are cleared as for
any file with capabilities.
This broke non-root containers that run setcap binaries with
allowPrivilegeEscalation: false: the binary started with no
capabilities at all.
Drop the special case. The existing no_new_privs downgrade already
matches Linux.
New exec tests (FileCaps*), Linux 6.12 vs runsc systrap:
Test Linux runsc before runsc after
FileCapsAlreadyHeldKept... PASS FAIL (1) PASS
FileCapsClearAmbient PASS PASS PASS
FileCapsClearAmbientWith... PASS FAIL (2) PASS
FileCapsNotGained... PASS PASS PASS
(1) permitted: got 0, want 400
(2) ambient kept: permitted got 400 (NET_BIND_SERVICE),
want 1 (CHOWN)
FileCapsClearAmbient is the same as (2) without no_new_privs.
Fixes google#14878
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thanks, the behavior is in line with Linux with the change |
milantracy
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Sep 25, 2026
milantracy
approved these changes
Sep 25, 2026
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Sep 25, 2026
Ambient capability support made execve ignore file capabilities when
no_new_privs is set. Linux does not do this. It skips setuid/setgid
bits under no_new_privs, but still applies file capabilities and only
stops them from adding to the permitted set. So capabilities the task
already holds are kept, and ambient capabilities are cleared as for
any file with capabilities.
This broke non-root containers that run setcap binaries with
allowPrivilegeEscalation: false: the binary started with no
capabilities at all.
Drop the special case. The existing no_new_privs downgrade already
matches Linux.
New exec tests (FileCaps*), Linux 6.12 vs runsc systrap:
Test Linux runsc before runsc after
FileCapsAlreadyHeldKept... PASS FAIL (1) PASS
FileCapsClearAmbient PASS PASS PASS
FileCapsClearAmbientWith... PASS FAIL (2) PASS
FileCapsNotGained... PASS PASS PASS
(1) permitted: got 0, want 400
(2) ambient kept: permitted got 400 (NET_BIND_SERVICE),
want 1 (CHOWN)
FileCapsClearAmbient is the same as (2) without no_new_privs.
Fixes #14878
FUTURE_COPYBARA_INTEGRATE_REVIEW=#14912 from shailend-g:nnp-fcaps aa481ad
PiperOrigin-RevId: 988018634
copybara-service Bot
pushed a commit
that referenced
this pull request
Sep 26, 2026
Ambient capability support made execve ignore file capabilities when
no_new_privs is set. Linux does not do this. It skips setuid/setgid
bits under no_new_privs, but still applies file capabilities and only
stops them from adding to the permitted set. So capabilities the task
already holds are kept, and ambient capabilities are cleared as for
any file with capabilities.
This broke non-root containers that run setcap binaries with
allowPrivilegeEscalation: false: the binary started with no
capabilities at all.
Drop the special case. The existing no_new_privs downgrade already
matches Linux.
New exec tests (FileCaps*), Linux 6.12 vs runsc systrap:
Test Linux runsc before runsc after
FileCapsAlreadyHeldKept... PASS FAIL (1) PASS
FileCapsClearAmbient PASS PASS PASS
FileCapsClearAmbientWith... PASS FAIL (2) PASS
FileCapsNotGained... PASS PASS PASS
(1) permitted: got 0, want 400
(2) ambient kept: permitted got 400 (NET_BIND_SERVICE),
want 1 (CHOWN)
FileCapsClearAmbient is the same as (2) without no_new_privs.
Fixes #14878
FUTURE_COPYBARA_INTEGRATE_REVIEW=#14912 from shailend-g:nnp-fcaps aa481ad
PiperOrigin-RevId: 988018634
copybara-service Bot
pushed a commit
that referenced
this pull request
Sep 26, 2026
Ambient capability support made execve ignore file capabilities when
no_new_privs is set. Linux does not do this. It skips setuid/setgid
bits under no_new_privs, but still applies file capabilities and only
stops them from adding to the permitted set. So capabilities the task
already holds are kept, and ambient capabilities are cleared as for
any file with capabilities.
This broke non-root containers that run setcap binaries with
allowPrivilegeEscalation: false: the binary started with no
capabilities at all.
Drop the special case. The existing no_new_privs downgrade already
matches Linux.
New exec tests (FileCaps*), Linux 6.12 vs runsc systrap:
Test Linux runsc before runsc after
FileCapsAlreadyHeldKept... PASS FAIL (1) PASS
FileCapsClearAmbient PASS PASS PASS
FileCapsClearAmbientWith... PASS FAIL (2) PASS
FileCapsNotGained... PASS PASS PASS
(1) permitted: got 0, want 400
(2) ambient kept: permitted got 400 (NET_BIND_SERVICE),
want 1 (CHOWN)
FileCapsClearAmbient is the same as (2) without no_new_privs.
Fixes #14878
FUTURE_COPYBARA_INTEGRATE_REVIEW=#14912 from shailend-g:nnp-fcaps aa481ad
PiperOrigin-RevId: 988018634
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Ambient capability support made execve ignore file capabilities when
no_new_privs is set. Linux does not do this. It skips setuid/setgid
bits under no_new_privs, but still applies file capabilities and only
stops them from adding to the permitted set. So capabilities the task
already holds are kept, and ambient capabilities are cleared as for
any file with capabilities.
This broke non-root containers that run setcap binaries with
allowPrivilegeEscalation: false: the binary started with no
capabilities at all.
Drop the special case. The existing no_new_privs downgrade already
matches Linux.
New exec tests (FileCaps*), Linux 6.12 vs runsc systrap:
FileCapsClearAmbient is the same as (2) without no_new_privs.
Fixes #14878