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Date: Thu, 18 Jun 2015 14:33:10 +0100
From: David Howells <dhowells@...hat.com>
To: sds@...ho.nsa.gov, viro@...iv.linux.org.uk, miklos@...redi.hu
Cc: linux-fsdevel@...r.kernel.org, dhowells@...hat.com,
linux-security-module@...r.kernel.org,
linux-unionfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 7/8] SELinux: Create a common helper to determine an inode
label
Create a common helper function to determine the label for a new inode. This
is then used by:
- may_create()
- selinux_dentry_init_security()
- selinux_inode_init_security()
- selinux_file_open_union()
This will change the behaviour of the first two functions slightly, bringing
them into line with the third. The fourth function is newly created in a
preceding patch and applied only in the case of a filesystem union or overlay.
Suggested-by: Stephen Smalley <sds@...ho.nsa.gov>
Signed-off-by: David Howells <dhowells@...hat.com>
---
security/selinux/hooks.c | 124 ++++++++++++++++++++++------------------------
1 file changed, 60 insertions(+), 64 deletions(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index c4495a797eb1..7eef1032c11a 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1684,6 +1684,42 @@ out:
return rc;
}
+/*
+ * Determine the label for an inode that might be unioned.
+ */
+static int selinux_determine_inode_label(const struct inode *dir,
+ const struct qstr *name,
+ const char *caller,
+ u16 tclass,
+ u32 *_new_isid)
+{
+ const struct superblock_security_struct *sbsec;
+ const struct inode_security_struct *dsec;
+ const struct task_security_struct *tsec = current_security();
+ int rc;
+
+ sbsec = dir->i_sb->s_security;
+
+ if ((sbsec->flags & SE_SBINITIALIZED) &&
+ (sbsec->behavior == SECURITY_FS_USE_MNTPOINT)) {
+ *_new_isid = sbsec->mntpoint_sid;
+ } else if (tsec->create_sid) {
+ *_new_isid = tsec->create_sid;
+ } else {
+ dsec = dir->i_security;
+
+ rc = security_transition_sid(tsec->sid, dsec->sid, tclass,
+ name, _new_isid);
+ if (rc) {
+ pr_warn("%s: security_transition_sid failed, rc=%d (name=%*.*s)\n",
+ caller, -rc, name->len, name->len, name->name);
+ return rc;
+ }
+ }
+
+ return 0;
+}
+
/* Check whether a task can create a file. */
static int may_create(struct inode *dir,
struct dentry *dentry,
@@ -1700,7 +1736,6 @@ static int may_create(struct inode *dir,
sbsec = dir->i_sb->s_security;
sid = tsec->sid;
- newsid = tsec->create_sid;
ad.type = LSM_AUDIT_DATA_DENTRY;
ad.u.dentry = dentry;
@@ -1711,12 +1746,10 @@ static int may_create(struct inode *dir,
if (rc)
return rc;
- if (!newsid || !(sbsec->flags & SBLABEL_MNT)) {
- rc = security_transition_sid(sid, dsec->sid, tclass,
- &dentry->d_name, &newsid);
- if (rc)
- return rc;
- }
+ rc = selinux_determine_inode_label(dir, &dentry->d_name, __func__,
+ tclass, &newsid);
+ if (rc)
+ return rc;
rc = avc_has_perm(sid, newsid, tclass, FILE__CREATE, &ad);
if (rc)
@@ -2723,32 +2756,14 @@ static int selinux_dentry_init_security(struct dentry *dentry, int mode,
struct qstr *name, void **ctx,
u32 *ctxlen)
{
- const struct cred *cred = current_cred();
- struct task_security_struct *tsec;
- struct inode_security_struct *dsec;
- struct superblock_security_struct *sbsec;
- struct inode *dir = d_backing_inode(dentry->d_parent);
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),
- name,
- &newsid);
- if (rc) {
- printk(KERN_WARNING
- "%s: security_transition_sid failed, rc=%d\n",
- __func__, -rc);
- return rc;
- }
- }
+ rc = selinux_determine_inode_label(d_inode(dentry), name, __func__,
+ inode_mode_to_security_class(mode),
+ &newsid);
+ if (rc)
+ return rc;
return security_sid_to_context(newsid, (char **)ctx, ctxlen);
}
@@ -2771,22 +2786,12 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
sid = tsec->sid;
newsid = tsec->create_sid;
- if ((sbsec->flags & SE_SBINITIALIZED) &&
- (sbsec->behavior == SECURITY_FS_USE_MNTPOINT))
- newsid = sbsec->mntpoint_sid;
- else if (!newsid || !(sbsec->flags & SBLABEL_MNT)) {
- rc = security_transition_sid(sid, dsec->sid,
- inode_mode_to_security_class(inode->i_mode),
- qstr, &newsid);
- if (rc) {
- printk(KERN_WARNING "%s: "
- "security_transition_sid failed, rc=%d (dev=%s "
- "ino=%ld)\n",
- __func__,
- -rc, inode->i_sb->s_id, inode->i_ino);
- return rc;
- }
- }
+ rc = selinux_determine_inode_label(
+ dir, qstr, __func__,
+ inode_mode_to_security_class(inode->i_mode),
+ &newsid);
+ if (rc)
+ return rc;
/* Possibly defer initialization to selinux_complete_init. */
if (sbsec->flags & SE_SBINITIALIZED) {
@@ -3502,9 +3507,7 @@ static int selinux_file_open_union(struct file *file,
struct file_security_struct *fsec,
const struct cred *cred)
{
- const struct superblock_security_struct *sbsec;
- const struct inode_security_struct *isec, *dsec, *fisec;
- const struct task_security_struct *tsec = current_security();
+ const struct inode_security_struct *isec, *fisec;
struct common_audit_data ad;
struct dentry *union_dentry = file->f_path.dentry;
const struct inode *union_inode = d_inode(union_dentry);
@@ -3512,29 +3515,22 @@ static int selinux_file_open_union(struct file *file,
struct dentry *dir;
int rc;
- sbsec = union_dentry->d_sb->s_security;
-
if (union_inode) {
+ /* If we're opening an overlay inode, use the label from that
+ * in preference to the label on a lower inode which we might
+ * actually be opening.
+ */
isec = union_inode->i_security;
fsec->union_isid = isec->sid;
- } else if ((sbsec->flags & SE_SBINITIALIZED) &&
- (sbsec->behavior == SECURITY_FS_USE_MNTPOINT)) {
- fsec->union_isid = sbsec->mntpoint_sid;
} else {
dir = dget_parent(union_dentry);
- dsec = d_inode(dir)->i_security;
-
- rc = security_transition_sid(
- tsec->sid, dsec->sid,
- inode_mode_to_security_class(lower_inode->i_mode),
+ rc = selinux_determine_inode_label(
+ d_inode(dir),
&union_dentry->d_name,
+ __func__,
+ inode_mode_to_security_class(lower_inode->i_mode),
&fsec->union_isid);
dput(dir);
- if (rc) {
- pr_warn("%s: security_transition_sid failed, rc=%d (name=%pD)\n",
- __func__, -rc, file);
- return rc;
- }
}
/* We need to check that the union file is allowed to be opened as well
--
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