On 2/14/19 4:50 AM, Ondrej Mosnacek wrote:
Since kernfs supports the security xattr handlers, we can simply use
these to determine the inode's context, dropping the need to update it
from kernfs explicitly using a security_inode_notifysecctx() call.
We achieve this by setting a new sbsec flag SE_SBGENFS_XATTR to all
mounts that are known to use kernfs under the hood and then fetching the
xattrs after determining the fallback genfs sid in
inode_doinit_with_dentry() when this flag is set.
This will allow implementing full security xattr support in kernfs and
removing the ...notifysecctx() call in a subsequent patch.
Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
---
security/selinux/hooks.c | 160 +++++++++++++++-------------
security/selinux/include/security.h | 1 +
2 files changed, 88 insertions(+), 73 deletions(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 81e012c66d95..7dea5b1a89a3 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -793,11 +793,13 @@ static int selinux_set_mnt_opts(struct super_block *sb,
if (!strcmp(sb->s_type->name, "debugfs") ||
!strcmp(sb->s_type->name, "tracefs") ||
- !strcmp(sb->s_type->name, "sysfs") ||
- !strcmp(sb->s_type->name, "pstore") ||
+ !strcmp(sb->s_type->name, "pstore"))
+ sbsec->flags |= SE_SBGENFS;
+
+ if (!strcmp(sb->s_type->name, "sysfs") ||
!strcmp(sb->s_type->name, "cgroup") ||
!strcmp(sb->s_type->name, "cgroup2"))
- sbsec->flags |= SE_SBGENFS;
+ sbsec->flags |= SE_SBGENFS | SE_SBGENFS_XATTR;
if (!sbsec->behavior) {
/*
@@ -1392,6 +1394,71 @@ static int selinux_genfs_get_sid(struct dentry *dentry,
return rc;
}
+static int inode_doinit_use_xattr(struct inode *inode, struct dentry *dentry,
+ u32 def_sid, u32 *sid)
+{
+#define INITCONTEXTLEN 255
+ char *context = NULL;
+ unsigned int len = 0;
No need to initialize here since no uses or gotos prior to first assignment?
+ int rc;
+
+ *sid = def_sid;
+
+ if (!(inode->i_opflags & IOP_XATTR))
+ return 0;
Is this a change in behavior from before the patch? Would we have
previously called __vfs_getxattr -> xattr_resolve_name and returned
either -EIO (is_bad_inode) or -EOPNOTSUPP to the caller? Perhaps it is
fine to return 0 with the default SID here, but wanted to check.
+
+ len = INITCONTEXTLEN;
+ context = kmalloc(len + 1, GFP_NOFS);
+ if (!context)
+ return -ENOMEM;
+
+ context[len] = '\0';
+ rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, context, len);
+ if (rc == -ERANGE) {
+ kfree(context);
+
+ /* Need a larger buffer. Query for the right size. */
+ rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, NULL, 0);
+ if (rc < 0)
+ return rc;
+
+ len = rc;
+ context = kmalloc(len + 1, GFP_NOFS);
+ if (!context)
+ return -ENOMEM;
+
+ context[len] = '\0';
+ rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX,
+ context, len);
+ }
+ if (rc < 0) {
+ kfree(context);
+ if (rc != -ENODATA) {
+ pr_warn("SELinux: %s: getxattr returned %d for dev=%s ino=%ld\n",
+ __func__, -rc, inode->i_sb->s_id, inode->i_ino);
+ return rc;
+ }
+ return 0;
+ }
+
+ rc = security_context_to_sid_default(&selinux_state, context, rc, sid,
+ def_sid, GFP_NOFS);
+ if (rc) {
+ char *dev = inode->i_sb->s_id;
+ unsigned long ino = inode->i_ino;
+
+ if (rc == -EINVAL) {
+ pr_notice_ratelimited("SELinux: inode=%lu on dev=%s was found to have an invalid context=%s. This indicates you may need to relabel the inode or the filesystem in question.\n",
+ ino, dev, context);
+ } else {
+ pr_warn("SELinux: %s: context_to_sid(%s) returned %d for dev=%s ino=%ld\n",
+ __func__, context, -rc, dev, ino);
+ }
+ }
+ kfree(context);
+ return 0;
+}
+
/* The inode's security attributes must be initialized before first use. */
static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dentry)
{
@@ -1400,9 +1467,6 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
u32 task_sid, sid = 0;
u16 sclass;
struct dentry *dentry;
-#define INITCONTEXTLEN 255
- char *context = NULL;
- unsigned len = 0;
int rc = 0;
if (isec->initialized == LABEL_INITIALIZED)
@@ -1470,72 +1534,11 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
goto out;
}
- len = INITCONTEXTLEN;
- context = kmalloc(len+1, GFP_NOFS);
- if (!context) {
- rc = -ENOMEM;
- dput(dentry);
- goto out;
- }
- context[len] = '\0';
- rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, context, len);
- if (rc == -ERANGE) {
- kfree(context);
-
- /* Need a larger buffer. Query for the right size. */
- rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, NULL, 0);
- if (rc < 0) {
- dput(dentry);
- goto out;
- }
- len = rc;
- context = kmalloc(len+1, GFP_NOFS);
- if (!context) {
- rc = -ENOMEM;
- dput(dentry);
- goto out;
- }
- context[len] = '\0';
- rc = __vfs_getxattr(dentry, inode, XATTR_NAME_SELINUX, context, len);
- }
+ rc = inode_doinit_use_xattr(inode, dentry, sbsec->def_sid,
+ &sid);
dput(dentry);
- if (rc < 0) {
- if (rc != -ENODATA) {
- pr_warn("SELinux: %s: getxattr returned "
- "%d for dev=%s ino=%ld\n", __func__,
- -rc, inode->i_sb->s_id, inode->i_ino);
- kfree(context);
- goto out;
- }
- /* Map ENODATA to the default file SID */
- sid = sbsec->def_sid;
- rc = 0;
- } else {
- rc = security_context_to_sid_default(&selinux_state,
- context, rc, &sid,
- sbsec->def_sid,
- GFP_NOFS);
- if (rc) {
- char *dev = inode->i_sb->s_id;
- unsigned long ino = inode->i_ino;
-
- if (rc == -EINVAL) {
- if (printk_ratelimit())
- pr_notice("SELinux: inode=%lu on dev=%s was found to have an invalid "
- "context=%s. This indicates you may need to relabel the inode or the "
- "filesystem in question.\n", ino, dev, context);
- } else {
- pr_warn("SELinux: %s: context_to_sid(%s) "
- "returned %d for dev=%s ino=%ld\n",
- __func__, context, -rc, dev, ino);
- }
- kfree(context);
- /* Leave with the unlabeled SID */
- rc = 0;
- break;
- }
- }
- kfree(context);
+ if (rc)
+ goto out;
break;
case SECURITY_FS_USE_TASK:
sid = task_sid;
@@ -1586,9 +1589,20 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
goto out;
rc = selinux_genfs_get_sid(dentry, sclass,
sbsec->flags, &sid);
- dput(dentry);
- if (rc)
+ if (rc) {
+ dput(dentry);
goto out;
+ }
+
+ if (sbsec->flags & SE_SBGENFS_XATTR) {
+ rc = inode_doinit_use_xattr(inode, dentry,
+ sid, &sid);
+ if (rc) {
+ dput(dentry);
+ goto out;
+ }
+ }
+ dput(dentry);
}
break;
}
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index f68fb25b5702..6e5928f951da 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -58,6 +58,7 @@
#define SE_SBINITIALIZED 0x0100
#define SE_SBPROC 0x0200
#define SE_SBGENFS 0x0400
+#define SE_SBGENFS_XATTR 0x0800
#define CONTEXT_STR "context="
#define FSCONTEXT_STR "fscontext="
