[PATCH v5 29/38] Smack: Abstract use of file security blob

From: Casey Schaufler
Date: Tue Dec 11 2018 - 17:45:01 EST


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

Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
security/smack/smack.h | 5 +++++
security/smack/smack_lsm.c | 12 ++++++++----
2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/security/smack/smack.h b/security/smack/smack.h
index b27eb252e953..50854969a391 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -362,6 +362,11 @@ static inline struct task_smack *smack_cred(const struct cred *cred)
return cred->security + smack_blob_sizes.lbs_cred;
}

+static inline struct smack_known **smack_file(const struct file *file)
+{
+ return (struct smack_known **)&file->f_security;
+}
+
/*
* Is the directory transmuting?
*/
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 459f7d523ca6..3e11be8cce7e 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1573,9 +1573,9 @@ static void smack_inode_getsecid(struct inode *inode, u32 *secid)
*/
static int smack_file_alloc_security(struct file *file)
{
- struct smack_known *skp = smk_of_current();
+ struct smack_known **blob = smack_file(file);

- file->f_security = skp;
+ *blob = smk_of_current();
return 0;
}

@@ -1815,7 +1815,9 @@ static int smack_mmap_file(struct file *file,
*/
static void smack_file_set_fowner(struct file *file)
{
- file->f_security = smk_of_current();
+ struct smack_known **blob = smack_file(file);
+
+ *blob = smk_of_current();
}

/**
@@ -1832,6 +1834,7 @@ static void smack_file_set_fowner(struct file *file)
static int smack_file_send_sigiotask(struct task_struct *tsk,
struct fown_struct *fown, int signum)
{
+ struct smack_known **blob;
struct smack_known *skp;
struct smack_known *tkp = smk_of_task(smack_cred(tsk->cred));
const struct cred *tcred;
@@ -1845,7 +1848,8 @@ static int smack_file_send_sigiotask(struct task_struct *tsk,
file = container_of(fown, struct file, f_owner);

/* we don't log here as rc can be overriden */
- skp = file->f_security;
+ blob = smack_file(file);
+ skp = *blob;
rc = smk_access(skp, tkp, MAY_DELIVER, NULL);
rc = smk_bu_note("sigiotask", skp, tkp, MAY_DELIVER, rc);

--
2.14.5