linux-kernel - [PATCH 3.16 156/328] apparmor: remove no-op permission check in policy

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Message-ID: <lsq.1544392233.181027988@decadent.org.uk>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Dan Carpenter" <dan.carpenter@...cle.com>,
        "John Johansen" <john.johansen@...onical.com>
Subject: [PATCH 3.16 156/328] apparmor: remove no-op permission check in
 policy_unpack

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: John Johansen <john.johansen@...onical.com>

commit c037bd615885f1d9d3bdb48531bace79fae1505d upstream.

The patch 736ec752d95e: "AppArmor: policy routines for loading and
unpacking policy" from Jul 29, 2010, leads to the following static
checker warning:

    security/apparmor/policy_unpack.c:410 verify_accept()
    warn: bitwise AND condition is false here

    security/apparmor/policy_unpack.c:413 verify_accept()
    warn: bitwise AND condition is false here

security/apparmor/policy_unpack.c
   392  #define DFA_VALID_PERM_MASK             0xffffffff
   393  #define DFA_VALID_PERM2_MASK            0xffffffff
   394
   395  /**
   396   * verify_accept - verify the accept tables of a dfa
   397   * @dfa: dfa to verify accept tables of (NOT NULL)
   398   * @flags: flags governing dfa
   399   *
   400   * Returns: 1 if valid accept tables else 0 if error
   401   */
   402  static bool verify_accept(struct aa_dfa *dfa, int flags)
   403  {
   404          int i;
   405
   406          /* verify accept permissions */
   407          for (i = 0; i < dfa->tables[YYTD_ID_ACCEPT]->td_lolen; i++) {
   408                  int mode = ACCEPT_TABLE(dfa)[i];
   409
   410                  if (mode & ~DFA_VALID_PERM_MASK)
   411                          return 0;
   412
   413                  if (ACCEPT_TABLE2(dfa)[i] & ~DFA_VALID_PERM2_MASK)
   414                          return 0;

fixes: 736ec752d95e ("AppArmor: policy routines for loading and unpacking policy")
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: John Johansen <john.johansen@...onical.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 security/apparmor/policy_unpack.c | 32 -------------------------------
 1 file changed, 32 deletions(-)

--- a/security/apparmor/policy_unpack.c
+++ b/security/apparmor/policy_unpack.c
@@ -290,32 +290,6 @@ static int unpack_strdup(struct aa_ext *
 	return res;
 }
 
-#define DFA_VALID_PERM_MASK		0xffffffff
-#define DFA_VALID_PERM2_MASK		0xffffffff
-
-/**
- * verify_accept - verify the accept tables of a dfa
- * @dfa: dfa to verify accept tables of (NOT NULL)
- * @flags: flags governing dfa
- *
- * Returns: 1 if valid accept tables else 0 if error
- */
-static bool verify_accept(struct aa_dfa *dfa, int flags)
-{
-	int i;
-
-	/* verify accept permissions */
-	for (i = 0; i < dfa->tables[YYTD_ID_ACCEPT]->td_lolen; i++) {
-		int mode = ACCEPT_TABLE(dfa)[i];
-
-		if (mode & ~DFA_VALID_PERM_MASK)
-			return 0;
-
-		if (ACCEPT_TABLE2(dfa)[i] & ~DFA_VALID_PERM2_MASK)
-			return 0;
-	}
-	return 1;
-}
 
 /**
  * unpack_dfa - unpack a file rule dfa
@@ -351,15 +325,9 @@ static struct aa_dfa *unpack_dfa(struct
 		if (IS_ERR(dfa))
 			return dfa;
 
-		if (!verify_accept(dfa, flags))
-			goto fail;
 	}
 
 	return dfa;
-
-fail:
-	aa_put_dfa(dfa);
-	return ERR_PTR(-EPROTO);
 }
 
 /**