From: Stephen Smalley <stephen.smalley.work@gmail.com>
Date: Tue, 10 Jun 2025 19:48:27 +0000 (-0400)
Subject: selinux: change security_compute_sid to return the ssid or tsid on match
X-Git-Tag: v6.16-rc4~33^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=fde46f60f6c5138ee422087addbc5bf5b4968bf1;p=thirdparty%2Flinux.git

selinux: change security_compute_sid to return the ssid or tsid on match

If the end result of a security_compute_sid() computation matches the
ssid or tsid, return that SID rather than looking it up again. This
avoids the problem of multiple initial SIDs that map to the same
context.

Cc: stable@vger.kernel.org
Reported-by: Guido Trentalancia <guido@trentalancia.com>
Fixes: ae254858ce07 ("selinux: introduce an initial SID for early boot processes")
Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Tested-by: Guido Trentalancia <guido@trentalancia.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
---

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 7becf3808818a..d185754c27862 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -1909,11 +1909,17 @@ retry:
 			goto out_unlock;
 	}
 	/* Obtain the sid for the context. */
-	rc = sidtab_context_to_sid(sidtab, &newcontext, out_sid);
-	if (rc == -ESTALE) {
-		rcu_read_unlock();
-		context_destroy(&newcontext);
-		goto retry;
+	if (context_equal(scontext, &newcontext))
+		*out_sid = ssid;
+	else if (context_equal(tcontext, &newcontext))
+		*out_sid = tsid;
+	else {
+		rc = sidtab_context_to_sid(sidtab, &newcontext, out_sid);
+		if (rc == -ESTALE) {
+			rcu_read_unlock();
+			context_destroy(&newcontext);
+			goto retry;
+		}
 	}
 out_unlock:
 	rcu_read_unlock();