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authorNeilBrown <neilb@suse.com>2018-01-03 08:01:15 +1100
committerJonathan Corbet <corbet@lwn.net>2018-01-08 14:20:31 -0700
commit0b345d722e07d77866edffcf350449a4607026b6 (patch)
tree3fa4dca4b1d05ecaf7257a5cec4b6bd0340032e0 /Documentation/security
parent536ec30477fe66d0564aff8f3595c8ce603f1411 (diff)
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Documentation: security/credentials.rst: explain need to sort group_list
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 <neilb@suse.com> [jc: use proper :c:func: references] Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/security')
-rw-r--r--Documentation/security/credentials.rst7
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/security/credentials.rst b/Documentation/security/credentials.rst
index 66a2e24939d8..5bb7125faeee 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 :c:func:`groups_sort` should be
+called before :c:func:`set_groups` or :c:func:`set_current_groups`.
+:c:func:`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::