linux-kernel - [PATCH 3.2 022/200] SELinux: Fix memory leak upon loading policy

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Message-ID: <lsq.1396221815.616209265@decadent.org.uk>
Date:	Mon, 31 Mar 2014 00:23:35 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Eric Paris" <eparis@...hat.com>,
	"Tetsuo Handa" <penguin-kernel@...ove.SAKURA.ne.jp>,
	"Paul Moore" <pmoore@...hat.com>
Subject: [PATCH 3.2 022/200] SELinux: Fix memory leak upon loading policy

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

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

From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

commit 8ed814602876bec9bad2649ca17f34b499357a1c upstream.

Hello.

I got below leak with linux-3.10.0-54.0.1.el7.x86_64 .

[  681.903890] kmemleak: 5538 new suspected memory leaks (see /sys/kernel/debug/kmemleak)

Below is a patch, but I don't know whether we need special handing for undoing
ebitmap_set_bit() call.
----------
>>>From fe97527a90fe95e2239dfbaa7558f0ed559c0992 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Date: Mon, 6 Jan 2014 16:30:21 +0900
Subject: [PATCH] SELinux: Fix memory leak upon loading policy

Commit 2463c26d "SELinux: put name based create rules in a hashtable" did not
check return value from hashtab_insert() in filename_trans_read(). It leaks
memory if hashtab_insert() returns error.

  unreferenced object 0xffff88005c9160d0 (size 8):
    comm "systemd", pid 1, jiffies 4294688674 (age 235.265s)
    hex dump (first 8 bytes):
      57 0b 00 00 6b 6b 6b a5                          W...kkk.
    backtrace:
      [<ffffffff816604ae>] kmemleak_alloc+0x4e/0xb0
      [<ffffffff811cba5e>] kmem_cache_alloc_trace+0x12e/0x360
      [<ffffffff812aec5d>] policydb_read+0xd1d/0xf70
      [<ffffffff812b345c>] security_load_policy+0x6c/0x500
      [<ffffffff812a623c>] sel_write_load+0xac/0x750
      [<ffffffff811eb680>] vfs_write+0xc0/0x1f0
      [<ffffffff811ec08c>] SyS_write+0x4c/0xa0
      [<ffffffff81690419>] system_call_fastpath+0x16/0x1b
      [<ffffffffffffffff>] 0xffffffffffffffff

However, we should not return EEXIST error to the caller, or the systemd will
show below message and the boot sequence freezes.

  systemd[1]: Failed to load SELinux policy. Freezing.

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Acked-by: Eric Paris <eparis@...hat.com>
Signed-off-by: Paul Moore <pmoore@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 security/selinux/ss/policydb.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -1914,7 +1914,19 @@ static int filename_trans_read(struct po
 		if (rc)
 			goto out;
 
-		hashtab_insert(p->filename_trans, ft, otype);
+		rc = hashtab_insert(p->filename_trans, ft, otype);
+		if (rc) {
+			/*
+			 * Do not return -EEXIST to the caller, or the system
+			 * will not boot.
+			 */
+			if (rc != -EEXIST)
+				goto out;
+			/* But free memory to avoid memory leak. */
+			kfree(ft);
+			kfree(name);
+			kfree(otype);
+		}
 	}
 	hash_eval(p->filename_trans, "filenametr");
 	return 0;

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