linux-kernel - [PATCH] uidgid: Make uid_valid and gid_valid work with !CONFIG

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Date:	Thu, 7 May 2015 12:26:33 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Iulia Manda <iulia.manda21@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Fabian Frederick <fabf@...net.be>,
	Peter Hurley <peter@...leysoftware.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] uidgid: Make uid_valid and gid_valid work with
 !CONFIG_MULTIUSER

{u,g}id_valid call {u,g}id_eq, which calls __k{u,g}id_val on both
arguments and compares.  With !CONFIG_MULTIUSER, __k{u,g}id_val return a
constant 0, which makes {u,g}id_valid always return false.  Change
{u,g}id_valid to compare their argument against -1 instead.  That
produces identical results in the normal CONFIG_MULTIUSER=y case, but
with !CONFIG_MULTIUSER will make {u,g}id_valid constant-fold into
"return true;" rather than "return false;".

This fixes uses of devpts without CONFIG_MULTIUSER.

Signed-off-by: Josh Triplett <josh@...htriplett.org>
---
 include/linux/uidgid.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/uidgid.h b/include/linux/uidgid.h
index 0ee05da..0383552 100644
--- a/include/linux/uidgid.h
+++ b/include/linux/uidgid.h
@@ -109,12 +109,12 @@ static inline bool gid_lte(kgid_t left, kgid_t right)
 
 static inline bool uid_valid(kuid_t uid)
 {
-	return !uid_eq(uid, INVALID_UID);
+	return __kuid_val(uid) != (uid_t) -1;
 }
 
 static inline bool gid_valid(kgid_t gid)
 {
-	return !gid_eq(gid, INVALID_GID);
+	return __kgid_val(gid) != (gid_t) -1;
 }
 
 #ifdef CONFIG_USER_NS
-- 
2.1.4

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