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

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Submitter Andy Whitcroft
Date Feb. 1, 2012, 9:35 a.m.
Message ID <1328088957-27506-2-git-send-email-apw@canonical.com>
Download mbox | patch
Permalink /patch/138929/
State New
Headers show

Comments

Andy Whitcroft - Feb. 1, 2012, 9:35 a.m.
From: Mimi Zohar <zohar@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:
  # PROC_SUPER_MAGIC
  dont_measure fsmagic=0x9fa0
  # SYSFS_MAGIC
  dont_measure fsmagic=0x62656572
  # DEBUGFS_MAGIC
  dont_measure fsmagic=0x64626720
  # TMPFS_MAGIC
  dont_measure fsmagic=0x01021994
  # SECURITYFS_MAGIC
  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@us.ibm.com>
Cc: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Cc: David Safford <safford@watson.ibm.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

(cherry picked from commit 867c20265459d30a01b021a9c1e81fb4c5832aa9)
CVE-2011-0006
BugLink: http://bugs.launchpad.net/bugs/917808
Signed-off-by: Andy Whitcroft <apw@canonical.com>
---
 security/integrity/ima/ima_policy.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
Stefan Bader - Feb. 1, 2012, 9:53 a.m.
On 01.02.2012 10:35, Andy Whitcroft wrote:
> From: Mimi Zohar <zohar@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:
>   # PROC_SUPER_MAGIC
>   dont_measure fsmagic=0x9fa0
>   # SYSFS_MAGIC
>   dont_measure fsmagic=0x62656572
>   # DEBUGFS_MAGIC
>   dont_measure fsmagic=0x64626720
>   # TMPFS_MAGIC
>   dont_measure fsmagic=0x01021994
>   # SECURITYFS_MAGIC
>   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@us.ibm.com>
> Cc: James Morris <jmorris@namei.org>
> Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
> Cc: David Safford <safford@watson.ibm.com>
> Cc: <stable@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> 
> (cherry picked from commit 867c20265459d30a01b021a9c1e81fb4c5832aa9)
> CVE-2011-0006
> BugLink: http://bugs.launchpad.net/bugs/917808
> Signed-off-by: Andy Whitcroft <apw@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,
>  					   &entry->lsm[lsm_rule].rule);
> +	if (!entry->lsm[lsm_rule].rule)
> +		return -EINVAL;
>  	return result;
>  }
>  
Checking something exists sounds like a good idea.

Acked-by: Stefan Bader <stefan.bader@canonical.com>
Herton Ronaldo Krzesinski - Feb. 1, 2012, 11:44 a.m.
On Wed, Feb 01, 2012 at 09:35:57AM +0000, Andy Whitcroft wrote:
> From: Mimi Zohar <zohar@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:
>   # PROC_SUPER_MAGIC
>   dont_measure fsmagic=0x9fa0
>   # SYSFS_MAGIC
>   dont_measure fsmagic=0x62656572
>   # DEBUGFS_MAGIC
>   dont_measure fsmagic=0x64626720
>   # TMPFS_MAGIC
>   dont_measure fsmagic=0x01021994
>   # SECURITYFS_MAGIC
>   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@us.ibm.com>
> Cc: James Morris <jmorris@namei.org>
> Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
> Cc: David Safford <safford@watson.ibm.com>
> Cc: <stable@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> 
> (cherry picked from commit 867c20265459d30a01b021a9c1e81fb4c5832aa9)
> CVE-2011-0006
> BugLink: http://bugs.launchpad.net/bugs/917808
> Signed-off-by: Andy Whitcroft <apw@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,
>  					   &entry->lsm[lsm_rule].rule);
> +	if (!entry->lsm[lsm_rule].rule)
> +		return -EINVAL;
>  	return result;
>  }
>  
> -- 
> 1.7.5.4
> 
> 
> -- 
> kernel-team mailing list
> kernel-team@lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team
>

Patch

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,
 					   &entry->lsm[lsm_rule].rule);
+	if (!entry->lsm[lsm_rule].rule)
+		return -EINVAL;
 	return result;
 }