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Subject[d_path 3/7] Add d_namespace_path() to compute namespace relative pathnames
In AppArmor, we are interested in pathnames relative to the namespace root.
This is the same as d_path() except for the root where the search ends. Add
a function for computing the namespace-relative path.

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Reviewed-by: John Johansen <jjohansen@suse.de>

---
fs/dcache.c | 6 +++---
fs/namespace.c | 27 +++++++++++++++++++++++++++
include/linux/dcache.h | 2 ++
include/linux/mount.h | 2 ++
4 files changed, 34 insertions(+), 3 deletions(-)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1750,9 +1750,9 @@ shouldnt_be_hashed:
*
* Returns the buffer or an error code.
*/
-static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
- struct dentry *root, struct vfsmount *rootmnt,
- char *buffer, int buflen, int fail_deleted)
+char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
+ struct dentry *root, struct vfsmount *rootmnt,
+ char *buffer, int buflen, int fail_deleted)
{
int namelen, is_slash, vfsmount_locked = 0;

--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1877,3 +1877,30 @@ void __put_mnt_ns(struct mnt_namespace *
release_mounts(&umount_list);
kfree(ns);
}
+
+char *d_namespace_path(struct dentry *dentry, struct vfsmount *vfsmnt,
+ char *buf, int buflen)
+{
+ struct vfsmount *rootmnt, *nsrootmnt = NULL;
+ struct dentry *root = NULL;
+ char *res;
+
+ read_lock(&current->fs->lock);
+ rootmnt = mntget(current->fs->rootmnt);
+ read_unlock(&current->fs->lock);
+ spin_lock(&vfsmount_lock);
+ if (rootmnt->mnt_ns)
+ nsrootmnt = mntget(rootmnt->mnt_ns->root);
+ spin_unlock(&vfsmount_lock);
+ mntput(rootmnt);
+ if (nsrootmnt)
+ root = dget(nsrootmnt->mnt_root);
+ res = __d_path(dentry, vfsmnt, root, nsrootmnt, buf, buflen, 1);
+ dput(root);
+ mntput(nsrootmnt);
+ /* Prevent empty path for lazily unmounted filesystems. */
+ if (!IS_ERR(res) && *res == '\0')
+ *--res = '.';
+ return res;
+}
+EXPORT_SYMBOL(d_namespace_path);
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -293,6 +293,8 @@ extern struct dentry * d_hash_and_lookup
/* validate "insecure" dentry pointer */
extern int d_validate(struct dentry *, struct dentry *);

+extern char *__d_path(struct dentry *, struct vfsmount *, struct dentry *,
+ struct vfsmount *, char *, int, int);
extern char * d_path(struct dentry *, struct vfsmount *, char *, int);

/* Allocation counts.. */
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -103,5 +103,7 @@ extern void shrink_submounts(struct vfsm
extern spinlock_t vfsmount_lock;
extern dev_t name_to_dev_t(char *name);

+extern char *d_namespace_path(struct dentry *, struct vfsmount *, char *, int);
+
#endif
#endif /* _LINUX_MOUNT_H */
--
Andreas Gruenbacher <agruen@suse.de>
SUSE Labs, SUSE LINUX Products GmbH
GF: Markus Rex, HRB 16746 (AG Nuernberg)

GPG: AF77 FAD1 1819 D442 400F 4BC8 409A 6903 4FDD EE02

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