[PATCH 3.2 073/125] auditsc: audit_krule mask accesses need bounds checking

Ben Hutchings
2014-07-08T19:24:25Z

From: Andy Lutomirski <luto@amacapital.net>

commit a3c54931199565930d6d84f4c3456f6440aefd41 upstream.

Fixes an easy DoS and possible information disclosure.

This does nothing about the broken state of x32 auditing.

eparis: If the admin has enabled auditd and has specifically loaded
audit rules. This bug has been around since before git. Wow...

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: audit_filter_inode_name() is not a separate
function but part of audit_filter_inodes()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
kernel/auditsc.c | 27 ++++++++++++++++++---------
1 file changed, 18 insertions(+), 9 deletions(-)

--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -688,6 +688,22 @@ static enum audit_state audit_filter_tas
return AUDIT_BUILD_CONTEXT;
}

+static int audit_in_mask(const struct audit_krule *rule, unsigned long val)
+{
+ int word, bit;
+
+ if (val > 0xffffffff)
+ return false;
+
+ word = AUDIT_WORD(val);
+ if (word >= AUDIT_BITMASK_SIZE)
+ return false;
+
+ bit = AUDIT_BIT(val);
+
+ return rule->mask[word] & bit;
+}
+
/* At syscall entry and exit time, this filter is called if the
* audit_state is not low enough that auditing cannot take place, but is
* also not high enough that we already know we have to write an audit
@@ -705,11 +721,8 @@ static enum audit_state audit_filter_sys

rcu_read_lock();
if (!list_empty(list)) {
- int word = AUDIT_WORD(ctx->major);
- int bit = AUDIT_BIT(ctx->major);
-
list_for_each_entry_rcu(e, list, list) {
- if ((e->rule.mask[word] & bit) == bit &&
+ if (audit_in_mask(&e->rule, ctx->major) &&
audit_filter_rules(tsk, &e->rule, ctx, NULL,
&state, false)) {
rcu_read_unlock();
@@ -738,8 +751,6 @@ void audit_filter_inodes(struct task_str

rcu_read_lock();
for (i = 0; i < ctx->name_count; i++) {
- int word = AUDIT_WORD(ctx->major);
- int bit = AUDIT_BIT(ctx->major);
struct audit_names *n = &ctx->names[i];
int h = audit_hash_ino((u32)n->ino);
struct list_head *list = &audit_inode_hash[h];
@@ -748,7 +759,7 @@ void audit_filter_inodes(struct task_str
continue;

list_for_each_entry_rcu(e, list, list) {
- if ((e->rule.mask[word] & bit) == bit &&
+ if (audit_in_mask(&e->rule, ctx->major) &&
audit_filter_rules(tsk, &e->rule, ctx, n,
&state, false)) {
rcu_read_unlock();