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    SubjectRe: [PATCH 01/12] Miscellaneous functions and defines needed by AppArmor, including the base path resolution routines.
    Al Viro wrote:
    > On Fri, Feb 19, 2010 at 01:36:17AM -0800, john.johansen@canonical.com wrote:
    >
    >> + spin_lock(&dcache_lock);
    >> + /* There is a race window between path lookup here and the
    >> + * need to strip the " (deleted) string that __d_path applies
    >> + * Detect the race and relookup the path
    >> + *
    >> + * The stripping of (deleted) is a hack that could be removed
    >> + * with an updated __d_path
    >
    > Yes, it could. Where's the patch doing just that? Or discussion of
    > desired interface, at lease...
    >
    Glad you asked I was going to include it with a couple other patches to
    __d_path. Basically trying to separate proposed changes to __d_path
    from AppArmor, as most people who will be looking at the __d_path code
    would rather not have the whole AppArmor patchset dropped on them.

    The attached patch is just a first pass and a starting point for
    discussion. I only modified TOMOYO to match current behavior of the
    kernel and will leave it to Tetsuo to modify TOMOYO to make use
    of the flag.

    ---

    Make __d_path unambiguous for deleted files

    __d_path currently appends the string " (deleted)" to deleted entries, but
    this results in an ambiguous path. This is problematic for TOMOYO and
    AppArmor as they use __d_path to retrieve path names for file objects.

    This patch matches the appending the " (deleted)" string optional,
    removing the need for AppArmor and TOMOYO to remove the string after
    the fact.

    Signed-off-by: John Johansen <john.johansen@canonical.com>

    diff --git a/fs/dcache.c b/fs/dcache.c
    index df49666..44c2afc 100644
    --- a/fs/dcache.c
    +++ b/fs/dcache.c
    @@ -1890,9 +1890,10 @@ static int prepend_name(char **buffer, int *buflen, struct qstr *name)
    * @root: root vfsmnt/dentry (may be modified by this function)
    * @buffer: buffer to return value in
    * @buflen: buffer length
    - *
    + * @mark_deleted: for deleted entries determine whether to append " (deleted)"
    * Convert a dentry into an ASCII path name. If the entry has been deleted
    - * the string " (deleted)" is appended. Note that this is ambiguous.
    + * and @mark_deleted is true then the string " (deleted)" is appended.
    + * Note that this is ambiguous.
    *
    * Returns a pointer into the buffer or an error code if the
    * path was too long.
    @@ -1903,7 +1904,7 @@ static int prepend_name(char **buffer, int *buflen, struct qstr *name)
    * root is changed (without modifying refcounts).
    */
    char *__d_path(const struct path *path, struct path *root,
    - char *buffer, int buflen)
    + char *buffer, int buflen, bool mark_deleted)
    {
    struct dentry *dentry = path->dentry;
    struct vfsmount *vfsmnt = path->mnt;
    @@ -1912,7 +1913,7 @@ char *__d_path(const struct path *path, struct path *root,

    spin_lock(&vfsmount_lock);
    prepend(&end, &buflen, "\0", 1);
    - if (d_unlinked(dentry) &&
    + if (d_unlinked(dentry) && mark_deleted &&
    (prepend(&end, &buflen, " (deleted)", 10) != 0))
    goto Elong;

    @@ -2019,7 +2020,7 @@ char *d_path(const struct path *path, char *buf, int buflen)
    read_unlock(&current->fs->lock);
    spin_lock(&dcache_lock);
    tmp = root;
    - res = __d_path(path, &tmp, buf, buflen);
    + res = __d_path(path, &tmp, buf, buflen, DPATH_MARK_DELETED);
    spin_unlock(&dcache_lock);
    path_put(&root);
    return res;
    @@ -2124,7 +2125,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
    struct path tmp = root;
    char * cwd;

    - cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE);
    + cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE, DPATH_MARK_DELETED);
    spin_unlock(&dcache_lock);

    error = PTR_ERR(cwd);
    diff --git a/fs/seq_file.c b/fs/seq_file.c
    index eae7d9d..f046bd3 100644
    --- a/fs/seq_file.c
    +++ b/fs/seq_file.c
    @@ -463,7 +463,7 @@ int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
    char *p;

    spin_lock(&dcache_lock);
    - p = __d_path(path, root, buf, size);
    + p = __d_path(path, root, buf, size, DPATH_MARK_DELETED);
    spin_unlock(&dcache_lock);
    res = PTR_ERR(p);
    if (!IS_ERR(p)) {
    diff --git a/include/linux/dcache.h b/include/linux/dcache.h
    index 30b93b2..021f515 100644
    --- a/include/linux/dcache.h
    +++ b/include/linux/dcache.h
    @@ -309,9 +309,12 @@ extern int d_validate(struct dentry *, struct dentry *);
    /*
    * helper function for dentry_operations.d_dname() members
    */
    +#define DPATH_MARK_DELETED 1
    +
    extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);

    -extern char *__d_path(const struct path *path, struct path *root, char *, int);
    +extern char *__d_path(const struct path *path, struct path *root, char *, int,
    + bool);
    extern char *d_path(const struct path *, char *, int);
    extern char *dentry_path(struct dentry *, char *, int);

    diff --git a/security/tomoyo/realpath.c b/security/tomoyo/realpath.c
    index 18369d4..0f4d4e2 100644
    --- a/security/tomoyo/realpath.c
    +++ b/security/tomoyo/realpath.c
    @@ -106,7 +106,8 @@ int tomoyo_realpath_from_path2(struct path *path, char *newname,
    spin_unlock(&vfsmount_lock);
    spin_lock(&dcache_lock);
    tmp = ns_root;
    - sp = __d_path(path, &tmp, newname, newname_len);
    + sp = __d_path(path, &tmp, newname, newname_len,
    + DPATH_MARK_DELETED);
    spin_unlock(&dcache_lock);
    path_put(&root);
    path_put(&ns_root);

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