65 lines
2.4 KiB
Plaintext
65 lines
2.4 KiB
Plaintext
|
From: John Johansen <john.johansen@canonical.com>
|
||
|
|
Date: Tue, 20 Jul 2010 06:57:08 -0700
|
||
|
|
Subject: AppArmor: Allow dfa backward compatibility with broken userspace
|
||
|
|
Patch-mainline: 2.6.37?
|
||
|
|
|
||
|
|
The apparmor_parser when compiling policy could generate invalid dfas
|
||
|
|
that did not have sufficient padding to avoid invalid references, when
|
||
|
|
used by the kernel. The kernels check to verify the next/check table
|
||
|
|
size was broken meaning invalid dfas were being created by userspace
|
||
|
|
and not caught.
|
||
|
|
|
||
|
|
To remain compatible with old tools that are not fixed, pad the loaded
|
||
|
|
dfas next/check table. The dfa's themselves are valid except for the
|
||
|
|
high padding for potentially invalid transitions (high bounds error),
|
||
|
|
which have a maximimum is 256 entries. So just allocate an extra null filled
|
||
|
|
256 entries for the next/check tables. This will guarentee all bounds
|
||
|
|
are good and invalid transitions go to the null (0) state.
|
||
|
|
|
||
|
|
Signed-off-by: John Johansen <john.johansen@canonical.com>
|
||
|
|
Acked-by: Jeff Mahoney <jeffm@suse.com>
|
||
|
|
---
|
||
|
|
security/apparmor/match.c | 17 +++++++++++++++++
|
||
|
|
1 file changed, 17 insertions(+)
|
||
|
|
|
||
|
|
--- a/security/apparmor/match.c
|
||
|
|
+++ b/security/apparmor/match.c
|
||
|
|
@@ -57,8 +57,17 @@ static struct table_header *unpack_table
|
||
|
|
if (bsize < tsize)
|
||
|
|
goto out;
|
||
|
|
|
||
|
|
+ /* Pad table allocation for next/check by 256 entries to remain
|
||
|
|
+ * backwards compatible with old (buggy) tools and remain safe without
|
||
|
|
+ * run time checks
|
||
|
|
+ */
|
||
|
|
+ if (th.td_id == YYTD_ID_NXT || th.td_id == YYTD_ID_CHK)
|
||
|
|
+ tsize += 256 * th.td_flags;
|
||
|
|
+
|
||
|
|
table = kvmalloc(tsize);
|
||
|
|
if (table) {
|
||
|
|
+ /* ensure the pad is clear, else there will be errors */
|
||
|
|
+ memset(table, 0, tsize);
|
||
|
|
*table = th;
|
||
|
|
if (th.td_flags == YYTD_DATA8)
|
||
|
|
UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
|
||
|
|
@@ -134,11 +143,19 @@ static int verify_dfa(struct aa_dfa *dfa
|
||
|
|
goto out;
|
||
|
|
|
||
|
|
if (flags & DFA_FLAG_VERIFY_STATES) {
|
||
|
|
+ int warning = 0;
|
||
|
|
for (i = 0; i < state_count; i++) {
|
||
|
|
if (DEFAULT_TABLE(dfa)[i] >= state_count)
|
||
|
|
goto out;
|
||
|
|
/* TODO: do check that DEF state recursion terminates */
|
||
|
|
if (BASE_TABLE(dfa)[i] + 255 >= trans_count) {
|
||
|
|
+ if (warning)
|
||
|
|
+ continue;
|
||
|
|
+ printk(KERN_WARNING "AppArmor DFA next/check "
|
||
|
|
+ "upper bounds error fixed, upgrade "
|
||
|
|
+ "user space tools \n");
|
||
|
|
+ warning = 1;
|
||
|
|
+ } else if (BASE_TABLE(dfa)[i] >= trans_count) {
|
||
|
|
printk(KERN_ERR "AppArmor DFA next/check upper "
|
||
|
|
"bounds error\n");
|
||
|
|
goto out;
|