This patch updates the documentation with the observations that led
to commit bdcf0a423ea1 ("kernel: make groups_sort calling a
responsibility group_info allocators") and the new behaviour required.
Specifically that groups_sort() should be called on a new group_list
before set_groups() or set_current_groups() is called.Signed-off-by: NeilBrown <ne...@suse.com> --- Documentation/security/credentials.rst | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/Documentation/security/credentials.rst b/Documentation/security/credentials.rst index 66a2e24939d8..5d659e3e52ad 100644 --- a/Documentation/security/credentials.rst +++ b/Documentation/security/credentials.rst @@ -451,6 +451,13 @@ checks and hooks done. Both the current and the proposed sets of credentials are available for this purpose as current_cred() will return the current set still at this point. +When replacing the group list, the new list must be sorted before it +is added to the credential, as a binary search is used to test for +membership. In practice, this means ``groups_sort()`` should be +called before ``set_groups()`` or ``set_current_groups()``. +``groups_sort()`` must not be called on a ``struct group_list`` which +is shared as it may permute elements as part of the sorting process +even if the array is already sorted. When the credential set is ready, it should be committed to the current process by calling:: -- 2.14.0.rc0.dirty
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