proc: implement /proc/[pid]/setgroups#13200
Open
copybara-service[bot] wants to merge 1 commit into
Open
Conversation
copybara-service
Bot
force-pushed
the
test/cl916335886
branch
2 times, most recently
from
a48548d to
24f14da
Compare
Without /proc/[pid]/setgroups the canonical rootless user-namespace setup cannot run. The expected sequence starts by writing "deny" to /proc/self/setgroups so that an unprivileged process can then write a non-trivial gid_map, and that file did not exist in gVisor. Tools that take this path, like buildah or podman, fail with ENOENT on /proc/[pid]/setgroups before they can do any work. I followed kernel/user_namespace.c. Each UserNamespace now carries a setgroupsAllowed bit that is initialized true and inherited from the parent at creation. Writing "deny" succeeds while gid_map is still empty and clears the bit, while writing "allow" succeeds only if the bit is still set, which preserves the one-way USERNS_SETGROUPS_ALLOWED transition. The unprivileged branch of SetGIDMap now requires the bit to be clear so that the behavior matches new_idmap_permitted, and setgroups(2) is gated by the conjunction of the bit and a non-empty gid_map, mirroring userns_may_setgroups. Tests in test/syscalls/linux/proc_pid_uid_gid_map.cc cover the file's read and write semantics, the one-way state transition, child-namespace inheritance, the syscall gating before and after deny, and the gid_map interaction. They pass on both runsc and native Linux. Closes #1235 and removes the b/27454212 TODO that has sat in user_namespace.go since the initial commit. FUTURE_COPYBARA_INTEGRATE_REVIEW=#13147 from shayonj:setgroups-impl 43f9528 PiperOrigin-RevId: 916335886
copybara-service
Bot
force-pushed
the
test/cl916335886
branch
from
24f14da to
6be50dc
Compare
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
proc: implement /proc/[pid]/setgroups
Without /proc/[pid]/setgroups the canonical rootless user-namespace setup
cannot run. The expected sequence starts by writing "deny" to
/proc/self/setgroups so that an unprivileged process can then write a
non-trivial gid_map, and that file did not exist in gVisor. Tools that
take this path, like buildah or podman, fail with ENOENT on
/proc/[pid]/setgroups before they can do any work.
I followed kernel/user_namespace.c. Each UserNamespace now carries a
setgroupsAllowed bit that is initialized true and inherited from the
parent at creation. Writing "deny" succeeds while gid_map is still empty
and clears the bit, while writing "allow" succeeds only if the bit is
still set, which preserves the one-way USERNS_SETGROUPS_ALLOWED
transition. The unprivileged branch of SetGIDMap now requires the bit to
be clear so that the behavior matches new_idmap_permitted, and
setgroups(2) is gated by the conjunction of the bit and a non-empty
gid_map, mirroring userns_may_setgroups.
Tests in test/syscalls/linux/proc_pid_uid_gid_map.cc cover the file's
read and write semantics, the one-way state transition, child-namespace
inheritance, the syscall gating before and after deny, and the gid_map
interaction. They pass on both runsc and native Linux.
Closes #1235 and removes the b/27454212 TODO that has sat in user_namespace.go since the initial commit.
FUTURE_COPYBARA_INTEGRATE_REVIEW=#13147 from shayonj:setgroups-impl 43f9528