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From: David P. Quigley on 7 Jul 2010 11:10
There is a time where we need to calculate a context without the
inode having been created yet. To do this we take the negative dentry and
calculate a context based on the process and the parent directory contexts.

Signed-off-by: Matthew N. Dodd <Matthew.Dodd(a)sparta.com>
Signed-off-by: David P. Quigley <dpquigl(a)tycho.nsa.gov>
---
include/linux/security.h | 22 ++++++++++++++++++++++
security/capability.c | 6 ++++++
security/security.c | 7 +++++++
security/selinux/hooks.c | 32 ++++++++++++++++++++++++++++++++
4 files changed, 67 insertions(+), 0 deletions(-)

diff --git a/include/linux/security.h b/include/linux/security.h
index 3158dd9..4d01784 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -322,6 +322,14 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
* Parse a string of security data filling in the opts structure
* @options string containing all mount options known by the LSM
* @opts binary data structure usable by the LSM
+ * @dentry_init_security:
+ * Compute a context for a dentry as the inode is not yet available
+ * since NFSv4 has no label backed by an EA anyway.
+ * @dentry dentry to use in calculating the context.
+ * @mode mode used to determine resource type.
+ * @ctx pointer to place the pointer to the resulting context in.
+ * @ctxlen point to place the length of the resulting context.
+ *
*
* Security hooks for inode operations.
*
@@ -1501,6 +1509,9 @@ struct security_operations {
void (*sb_clone_mnt_opts) (const struct super_block *oldsb,
struct super_block *newsb);
int (*sb_parse_opts_str) (char *options, struct security_mnt_opts *opts);
+ int (*dentry_init_security) (struct dentry *dentry, int mode,
+ void **ctx, u32 *ctxlen);
+

#ifdef CONFIG_SECURITY_PATH
int (*path_unlink) (struct path *dir, struct dentry *dentry);
@@ -1795,6 +1806,8 @@ int security_sb_set_mnt_opts(struct super_block *sb, struct security_mnt_opts *o
void security_sb_clone_mnt_opts(const struct super_block *oldsb,
struct super_block *newsb);
int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts);
+int security_dentry_init_security (struct dentry *dentry, int mode,
+ void **ctx, u32 *ctxlen);

int security_inode_alloc(struct inode *inode);
void security_inode_free(struct inode *inode);
@@ -2157,6 +2170,15 @@ static inline int security_inode_alloc(struct inode *inode)
static inline void security_inode_free(struct inode *inode)
{ }

+static inline int security_dentry_init_security (struct dentry *dentry,
+ int mode,
+ void **ctx,
+ u32 *ctxlen)
+{
+ return -EOPNOTSUPP;
+}
+
+
static inline int security_inode_init_security(struct inode *inode,
struct inode *dir,
char **name,
diff --git a/security/capability.c b/security/capability.c
index 4875142..9ce1c2f 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -134,6 +134,11 @@ static int cap_sb_parse_opts_str(char *options, struct security_mnt_opts *opts)
return 0;
}

+static int cap_dentry_init_security(struct dentry *dentry, int mode, void **ctx, u32 *ctxlen)
+{
+ return 0;
+}
+
static int cap_inode_alloc_security(struct inode *inode)
{
return 0;
@@ -952,6 +957,7 @@ void security_fixup_ops(struct security_operations *ops)
set_to_cap_if_null(ops, sb_set_mnt_opts);
set_to_cap_if_null(ops, sb_clone_mnt_opts);
set_to_cap_if_null(ops, sb_parse_opts_str);
+ set_to_cap_if_null(ops, dentry_init_security);
set_to_cap_if_null(ops, inode_alloc_security);
set_to_cap_if_null(ops, inode_free_security);
set_to_cap_if_null(ops, inode_init_security);
diff --git a/security/security.c b/security/security.c
index 687c6fd..c1b6847 100644
--- a/security/security.c
+++ b/security/security.c
@@ -386,6 +386,13 @@ void security_inode_free(struct inode *inode)
security_ops->inode_free_security(inode);
}

+int security_dentry_init_security (struct dentry *dentry, int mode,
+ void **ctx, u32 *ctxlen)
+{
+ return security_ops->dentry_init_security (dentry, mode, ctx, ctxlen);
+}
+EXPORT_SYMBOL(security_dentry_init_security);
+
int security_inode_init_security(struct inode *inode, struct inode *dir,
char **name, void **value, size_t *len)
{
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 5feecb4..435c51f 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2577,6 +2577,37 @@ static void selinux_inode_free_security(struct inode *inode)
inode_free_security(inode);
}

+static int selinux_dentry_init_security(struct dentry *dentry, int mode, void **ctx, u32 *ctxlen)
+{
+ struct cred *cred = current_cred();
+ struct task_security_struct *tsec;
+ struct inode_security_struct *dsec;
+ struct superblock_security_struct *sbsec;
+ struct inode *dir = dentry->d_parent->d_inode;
+ u32 newsid;
+ int rc;
+
+ tsec = cred->security;
+ dsec = dir->i_security;
+ sbsec = dir->i_sb->s_security;
+
+ if (tsec->create_sid && sbsec->behavior != SECURITY_FS_USE_MNTPOINT) {
+ newsid = tsec->create_sid;
+ } else {
+ rc = security_transition_sid(tsec->sid, dsec->sid,
+ inode_mode_to_security_class(mode),
+ &newsid);
+ if (rc) {
+ printk(KERN_WARNING "%s: "
+ "security_transition_sid failed, rc=%d\n",
+ __FUNCTION__, -rc);
+ return rc;
+ }
+ }
+
+ return security_sid_to_context(newsid, (char **)ctx, ctxlen);
+}
+
static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
char **name, void **value,
size_t *len)
@@ -5484,6 +5515,7 @@ static struct security_operations selinux_ops = {
.sb_clone_mnt_opts = selinux_sb_clone_mnt_opts,
.sb_parse_opts_str = selinux_parse_opts_str,

+ .dentry_init_security = selinux_dentry_init_security,

.inode_alloc_security = selinux_inode_alloc_security,
.inode_free_security = selinux_inode_free_security,
--
1.6.2.5

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