[maverick/ti-omap4 CVE 1/1] ima: fix add LSM rule bug

Andy Whitcroft apw at canonical.com
Wed Feb 1 09:35:57 UTC 2012

From: Mimi Zohar <zohar at linux.vnet.ibm.com>

If security_filter_rule_init() doesn't return a rule, then not everything
is as fine as the return code implies.

This bug only occurs when the LSM (eg. SELinux) is disabled at runtime.

Adding an empty LSM rule causes ima_match_rules() to always succeed,
ignoring any remaining rules.

 default IMA TCB policy:
  dont_measure fsmagic=0x9fa0
  dont_measure fsmagic=0x62656572
  dont_measure fsmagic=0x64626720
  dont_measure fsmagic=0x01021994
  dont_measure fsmagic=0x73636673

  < LSM specific rule >
  dont_measure obj_type=var_log_t

  measure func=BPRM_CHECK
  measure func=FILE_MMAP mask=MAY_EXEC
  measure func=FILE_CHECK mask=MAY_READ uid=0

Thus without the patch, with the boot parameters 'tcb selinux=0', adding
the above 'dont_measure obj_type=var_log_t' rule to the default IMA TCB
measurement policy, would result in nothing being measured.  The patch
prevents the default TCB policy from being replaced.

Signed-off-by: Mimi Zohar <zohar at us.ibm.com>
Cc: James Morris <jmorris at namei.org>
Acked-by: Serge Hallyn <serge.hallyn at canonical.com>
Cc: David Safford <safford at watson.ibm.com>
Cc: <stable at kernel.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>

(cherry picked from commit 867c20265459d30a01b021a9c1e81fb4c5832aa9)
BugLink: http://bugs.launchpad.net/bugs/917808
Signed-off-by: Andy Whitcroft <apw at canonical.com>
 security/integrity/ima/ima_policy.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index aef8c0a..d661afb 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -253,6 +253,8 @@ static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
 	result = security_filter_rule_init(entry->lsm[lsm_rule].type,
 					   Audit_equal, args,
+	if (!entry->lsm[lsm_rule].rule)
+		return -EINVAL;
 	return result;

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