Previously, path_init's handling of *at(dfd, ...) was only done once, but with LOOKUP_BENEATH (and LOOKUP_IN_ROOT) we have to parse the initial nd->path at different times (before or after absolute path handling) depending on whether we have been asked to scope resolution within a root.
Signed-off-by: Aleksa Sarai cyphar@cyphar.com --- fs/namei.c | 103 ++++++++++++++++++++++++++++++----------------------- 1 file changed, 59 insertions(+), 44 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c index 46c5302eea4a..dc323e25d4d2 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2251,9 +2251,59 @@ static int link_path_walk(const char *name, struct nameidata *nd) } }
+/* + * Configure nd->path based on the nd->dfd. This is only used as part of + * path_init(). + */ +static inline int dirfd_path_init(struct nameidata *nd) +{ + if (nd->dfd == AT_FDCWD) { + if (nd->flags & LOOKUP_RCU) { + struct fs_struct *fs = current->fs; + unsigned seq; + + do { + seq = read_seqcount_begin(&fs->seq); + nd->path = fs->pwd; + nd->inode = nd->path.dentry->d_inode; + nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); + } while (read_seqcount_retry(&fs->seq, seq)); + } else { + get_fs_pwd(current->fs, &nd->path); + nd->inode = nd->path.dentry->d_inode; + } + } else { + /* Caller must check execute permissions on the starting path component */ + struct fd f = fdget_raw(nd->dfd); + struct dentry *dentry; + + if (!f.file) + return -EBADF; + + dentry = f.file->f_path.dentry; + + if (*nd->name->name && unlikely(!d_can_lookup(dentry))) { + fdput(f); + return -ENOTDIR; + } + + nd->path = f.file->f_path; + if (nd->flags & LOOKUP_RCU) { + nd->inode = nd->path.dentry->d_inode; + nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); + } else { + path_get(&nd->path); + nd->inode = nd->path.dentry->d_inode; + } + fdput(f); + } + return 0; +} + /* must be paired with terminate_walk() */ static const char *path_init(struct nameidata *nd, unsigned flags) { + int error; const char *s = nd->name->name;
if (!*s) @@ -2287,52 +2337,17 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
nd->m_seq = read_seqbegin(&mount_lock); if (*s == '/') { - set_root(nd); - if (likely(!nd_jump_root(nd))) - return s; - return ERR_PTR(-ECHILD); - } else if (nd->dfd == AT_FDCWD) { - if (flags & LOOKUP_RCU) { - struct fs_struct *fs = current->fs; - unsigned seq; - - do { - seq = read_seqcount_begin(&fs->seq); - nd->path = fs->pwd; - nd->inode = nd->path.dentry->d_inode; - nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); - } while (read_seqcount_retry(&fs->seq, seq)); - } else { - get_fs_pwd(current->fs, &nd->path); - nd->inode = nd->path.dentry->d_inode; - } - return s; - } else { - /* Caller must check execute permissions on the starting path component */ - struct fd f = fdget_raw(nd->dfd); - struct dentry *dentry; - - if (!f.file) - return ERR_PTR(-EBADF); - - dentry = f.file->f_path.dentry; - - if (*s && unlikely(!d_can_lookup(dentry))) { - fdput(f); - return ERR_PTR(-ENOTDIR); - } - - nd->path = f.file->f_path; - if (flags & LOOKUP_RCU) { - nd->inode = nd->path.dentry->d_inode; - nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); - } else { - path_get(&nd->path); - nd->inode = nd->path.dentry->d_inode; - } - fdput(f); + if (likely(!nd->root.mnt)) + set_root(nd); + error = nd_jump_root(nd); + if (unlikely(error)) + s = ERR_PTR(error); return s; } + error = dirfd_path_init(nd); + if (unlikely(error)) + return ERR_PTR(error); + return s; }
static const char *trailing_symlink(struct nameidata *nd)