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.
Signed-off-by: Andrey Vagin <avagin@xxxxxxxxxx>
---
fs/namei.c | 12 +++++++++++-
include/linux/namei.h | 2 ++
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/fs/namei.c b/fs/namei.c
index 70580ab..5f08b69 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -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 +2174,11 @@ 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))
+ path_get(&nd->root);
+ }
return s;
} else {
/* Caller must check execute permissions on the starting path component */
@@ -2202,6 +2207,11 @@ 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))
+ path_get(&nd->root);
+ }
return s;
}
}
diff --git a/include/linux/namei.h b/include/linux/namei.h
index d3d0398..ca2ea13 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -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);
--
2.5.5
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
