linux-kernel - [PATCH] getgroups.2: Document unprivileged setgroups calls

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Message-ID: <20141115235017.GA31536@thin>
Date:	Sat, 15 Nov 2014 15:50:17 -0800
From:	Josh Triplett <josh@...htriplett.org>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Kees Cook <keescook@...omium.org>, mtk.manpages@...il.com,
	linux-api@...r.kernel.org, linux-man@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] getgroups.2: Document unprivileged setgroups calls

Signed-off-by: Josh Triplett <josh@...htriplett.org>
---
v3: Document use of gid/egid/sgid.
v2: Document requirement for no_new_privs.

(If this doesn't end up going into 3.18, the version number in the patch will
need updating.)

 man2/getgroups.2 | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/man2/getgroups.2 b/man2/getgroups.2
index 373c204..e2b834e 100644
--- a/man2/getgroups.2
+++ b/man2/getgroups.2
@@ -81,9 +81,16 @@ to be used in a further call to
 .PP
 .BR setgroups ()
 sets the supplementary group IDs for the calling process.
-Appropriate privileges (Linux: the
+A process with the
 .B CAP_SETGID
-capability) are required.
+capability may change its supplementary group IDs arbitrarily.
+As of Linux 3.18, any process that has enabled PR_SET_NO_NEW_PRIVS (see
+.BR prctl (2))
+may drop supplementary groups, or add any of the current real UID, the current
+effective UID, or the current saved set-user-ID; adding any other group ID
+requires the
+.B CAP_SETGID
+capability.
 The
 .I size
 argument specifies the number of supplementary group IDs
-- 
2.1.3

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