Re: [PATCH v4 02/19] Smack: Abstract use of cred security blob

[Kees Cook]

On Fri, Sep 21, 2018 at 5:17 PM, Casey Schaufler  wrote:
> Don't use the cred->security pointer directly.
> Provide a helper function that provides the security blob pointer.
>
> Signed-off-by: Casey Schaufler 

Reviewed-by: Kees Cook 

-Kees

-- 
Kees Cook
Pixel Security
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[PATCH v4 02/19] Smack: Abstract use of cred security blob

[Casey Schaufler]

Don't use the cred->security pointer directly.
Provide a helper function that provides the security blob pointer.

Signed-off-by: Casey Schaufler 
---
 security/smack/smack.h| 17 +--
 security/smack/smack_access.c |  4 +--
 security/smack/smack_lsm.c| 57 +--
 security/smack/smackfs.c  | 18 +--
 4 files changed, 53 insertions(+), 43 deletions(-)

diff --git a/security/smack/smack.h b/security/smack/smack.h
index f7db791fb566..01a922856eba 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -356,6 +356,11 @@ extern struct list_head smack_onlycap_list;
 #define SMACK_HASH_SLOTS 16
 extern struct hlist_head smack_known_hash[SMACK_HASH_SLOTS];
 
+static inline struct task_smack *smack_cred(const struct cred *cred)
+{
+   return cred->security;
+}
+
 /*
  * Is the directory transmuting?
  */
@@ -382,13 +387,19 @@ static inline struct smack_known *smk_of_task(const 
struct task_smack *tsp)
return tsp->smk_task;
 }
 
-static inline struct smack_known *smk_of_task_struct(const struct task_struct 
*t)
+static inline struct smack_known *smk_of_task_struct(
+   const struct task_struct *t)
 {
struct smack_known *skp;
+   const struct cred *cred;
 
rcu_read_lock();
-   skp = smk_of_task(__task_cred(t)->security);
+
+   cred = __task_cred(t);
+   skp = smk_of_task(smack_cred(cred));
+
rcu_read_unlock();
+
return skp;
 }
 
@@ -405,7 +416,7 @@ static inline struct smack_known *smk_of_forked(const 
struct task_smack *tsp)
  */
 static inline struct smack_known *smk_of_current(void)
 {
-   return smk_of_task(current_security());
+   return smk_of_task(smack_cred(current_cred()));
 }
 
 /*
diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
index 9a4c0ad46518..489d49a20b47 100644
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -275,7 +275,7 @@ int smk_tskacc(struct task_smack *tsp, struct smack_known 
*obj_known,
 int smk_curacc(struct smack_known *obj_known,
   u32 mode, struct smk_audit_info *a)
 {
-   struct task_smack *tsp = current_security();
+   struct task_smack *tsp = smack_cred(current_cred());
 
return smk_tskacc(tsp, obj_known, mode, a);
 }
@@ -635,7 +635,7 @@ DEFINE_MUTEX(smack_onlycap_lock);
  */
 bool smack_privileged_cred(int cap, const struct cred *cred)
 {
-   struct task_smack *tsp = cred->security;
+   struct task_smack *tsp = smack_cred(cred);
struct smack_known *skp = tsp->smk_task;
struct smack_known_list_elem *sklep;
int rc;
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 340fc30ad85d..68ee3ae8f25c 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -122,7 +122,7 @@ static int smk_bu_note(char *note, struct smack_known *sskp,
 static int smk_bu_current(char *note, struct smack_known *oskp,
  int mode, int rc)
 {
-   struct task_smack *tsp = current_security();
+   struct task_smack *tsp = smack_cred(current_cred());
char acc[SMK_NUM_ACCESS_TYPE + 1];
 
if (rc <= 0)
@@ -143,7 +143,7 @@ static int smk_bu_current(char *note, struct smack_known 
*oskp,
 #ifdef CONFIG_SECURITY_SMACK_BRINGUP
 static int smk_bu_task(struct task_struct *otp, int mode, int rc)
 {
-   struct task_smack *tsp = current_security();
+   struct task_smack *tsp = smack_cred(current_cred());
struct smack_known *smk_task = smk_of_task_struct(otp);
char acc[SMK_NUM_ACCESS_TYPE + 1];
 
@@ -165,7 +165,7 @@ static int smk_bu_task(struct task_struct *otp, int mode, 
int rc)
 #ifdef CONFIG_SECURITY_SMACK_BRINGUP
 static int smk_bu_inode(struct inode *inode, int mode, int rc)
 {
-   struct task_smack *tsp = current_security();
+   struct task_smack *tsp = smack_cred(current_cred());
struct inode_smack *isp = inode->i_security;
char acc[SMK_NUM_ACCESS_TYPE + 1];
 
@@ -195,7 +195,7 @@ static int smk_bu_inode(struct inode *inode, int mode, int 
rc)
 #ifdef CONFIG_SECURITY_SMACK_BRINGUP
 static int smk_bu_file(struct file *file, int mode, int rc)
 {
-   struct task_smack *tsp = current_security();
+   struct task_smack *tsp = smack_cred(current_cred());
struct smack_known *sskp = tsp->smk_task;
struct inode *inode = file_inode(file);
struct inode_smack *isp = inode->i_security;
@@ -225,7 +225,7 @@ static int smk_bu_file(struct file *file, int mode, int rc)
 static int smk_bu_credfile(const struct cred *cred, struct file *file,
int mode, int rc)
 {
-   struct task_smack *tsp = cred->security;
+   struct task_smack *tsp = smack_cred(cred);
struct smack_known *sskp = tsp->smk_task;
struct inode *inode = file_inode(file);
struct inode_smack *isp = inode->i_security;
@@ -429,7 +429,7 @@ static int