linux-kernel - [PATCH v3 4/7] selinux: make left shifts well defined

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Message-Id: <20230807171143.208481-3-cgzones@googlemail.com>
Date:   Mon,  7 Aug 2023 19:11:38 +0200
From:   Christian Göttsche <cgzones@...glemail.com>
To:     selinux@...r.kernel.org
Cc:     Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        "GONG, Ruiqi" <gongruiqi1@...wei.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v3 4/7] selinux: make left shifts well defined

The loops upper bound represent the number of permissions used (for the
current class or in general).  The limit for this is 32, thus we might
left shift of one less, 31.  Shifting a base of 1 results in undefined
behavior; use (u32)1 as base.

Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
---
v3: split from parent commit and apply cast to correct shift operand
---
 security/selinux/ss/services.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index dacec2ebdcd7..1eeffc66ea7d 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -207,22 +207,22 @@ static void map_decision(struct selinux_map *map,
 
 		for (i = 0, result = 0; i < n; i++) {
 			if (avd->allowed & mapping->perms[i])
-				result |= 1<<i;
+				result |= (u32)1<<i;
 			if (allow_unknown && !mapping->perms[i])
-				result |= 1<<i;
+				result |= (u32)1<<i;
 		}
 		avd->allowed = result;
 
 		for (i = 0, result = 0; i < n; i++)
 			if (avd->auditallow & mapping->perms[i])
-				result |= 1<<i;
+				result |= (u32)1<<i;
 		avd->auditallow = result;
 
 		for (i = 0, result = 0; i < n; i++) {
 			if (avd->auditdeny & mapping->perms[i])
-				result |= 1<<i;
+				result |= (u32)1<<i;
 			if (!allow_unknown && !mapping->perms[i])
-				result |= 1<<i;
+				result |= (u32)1<<i;
 		}
 		/*
 		 * In case the kernel has a bug and requests a permission
@@ -230,7 +230,7 @@ static void map_decision(struct selinux_map *map,
 		 * should audit that denial
 		 */
 		for (; i < (sizeof(u32)*8); i++)
-			result |= 1<<i;
+			result |= (u32)1<<i;
 		avd->auditdeny = result;
 	}
 }
-- 
2.40.1