@@ -2148,7 +2148,7 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
nd->path.dentry = NULL;
nd->m_seq = read_seqbegin(&mount_lock);
- if (*s == '/') {
+ if (*s == '/' && !(flags & LOOKUP_DFD_ROOT)) {
if (flags & LOOKUP_RCU)
rcu_read_lock();
set_root(nd);
@@ -2174,6 +2174,13 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
get_fs_pwd(current->fs, &nd->path);
nd->inode = nd->path.dentry->d_inode;
}
+ if (flags & LOOKUP_DFD_ROOT) {
+ nd->root = nd->path;
+ if (flags & LOOKUP_RCU)
+ nd->root_seq = nd->seq;
+ else
+ path_get(&nd->root);
+ }
return s;
} else {
/* Caller must check execute permissions on the starting path component */
@@ -2202,6 +2209,13 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
nd->inode = nd->path.dentry->d_inode;
}
fdput(f);
+ if (flags & LOOKUP_DFD_ROOT) {
+ nd->root = nd->path;
+ if (flags & LOOKUP_RCU)
+ nd->root_seq = nd->seq;
+ else
+ path_get(&nd->root);
+ }
return s;
}
}
@@ -45,6 +45,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
#define LOOKUP_ROOT 0x2000
#define LOOKUP_EMPTY 0x4000
+#define LOOKUP_DFD_ROOT 0x8000
+
extern int path_pts(struct path *path);
extern int user_path_at_empty(int, const char __user *, unsigned, struct path *, int *empty);
The problem is that a pathname can contain absolute symlinks and now they are resolved relative to the current root. If we want to open a file in another mount namespaces and we have a file descriptor to its root directory, we probably want to resolve pathname in the target mount namespace. For this we add this new flag. If LOOKUP_DFD_ROOT is set, path_init() initializes nd->root and nd->path to the same value. Changes since v1: * initialize nd->root_seq (thanks to Omar Sandoval for reporting and fixing this issue) Cc: Omar Sandoval <osandov@osandov.com> Signed-off-by: Andrey Vagin <avagin@openvz.org> --- fs/namei.c | 16 +++++++++++++++- include/linux/namei.h | 2 ++ 2 files changed, 17 insertions(+), 1 deletion(-)