On Thu, 9 Jun 2016 21:27:34 +0200 Marcus Hoffmann <marcus.hoffmann@xxxxxxxxxxxx> wrote: > Hey Aurélien, > with your script I can reproduce the bug locally now. Good. > I can mount the share (which is on a Windows 8.1 vm) with a Windows 7 > PC with the restricted user account. (Even in hard mode.) > I can mount the share from Linux-cifs using the admin user but not the > restricted user. I've moved some things around. All of the prefix path components are now checked for accessibility in cifs_do_mount(). This is more robust and it lets us set the CIFS_MOUNT_USE_PREFIX_PATH flag earlier. I've updated the cifs_root_iget() to use the prefix path when necessary which should take care of the last case (hard mode). Please test my latest patch (attached). > (I noticed though that no user has access to the file in the shared > dir. But this doesn't really matter for the test.) Indeed. -- Aurélien Aptel / SUSE Labs Samba Team GPG: 1839 CB5F 9F5B FB9B AA97 8C99 03C8 A49B 521B D5D3 SUSE Linux GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
From e858c28b7bf9b1c76c0a9703727c7bd02bf4a434 Mon Sep 17 00:00:00 2001
From: Aurelien Aptel <aaptel@xxxxxxxx>
Date: Wed, 25 May 2016 19:59:09 +0200
Subject: [PATCH] fs/cifs: make share unaccessible at root level mountable
if, when mounting //HOST/share/sub/dir/foo we can query /sub/dir/foo but
not any of the path components above:
- store the /sub/dir/foo prefix in the cifs super_block info
- in the superblock, set root dentry to the subpath dentry (instead of
the share root)
- set a flag in the superblock to remember it
- use prefixpath when building path from a dentry
fixes bso#8950
Signed-off-by: Aurelien Aptel <aaptel@xxxxxxxx>
---
fs/cifs/cifs_fs_sb.h | 2 ++
fs/cifs/cifsfs.c | 15 ++++++++++++++-
fs/cifs/connect.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
fs/cifs/dir.c | 19 +++++++++++++++++--
fs/cifs/inode.c | 17 +++++++++++++++--
5 files changed, 95 insertions(+), 5 deletions(-)
diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
index 3182273..02b9ac3 100644
--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -46,6 +46,7 @@
#define CIFS_MOUNT_CIFS_BACKUPUID 0x200000 /* backup intent bit for a user */
#define CIFS_MOUNT_CIFS_BACKUPGID 0x400000 /* backup intent bit for a group */
#define CIFS_MOUNT_MAP_SFM_CHR 0x800000 /* SFM/MAC mapping for illegal chars */
+#define CIFS_MOUNT_USE_PREFIX_PATH 0x1000000 /* make subpath with unaccessible root mountable */
struct cifs_sb_info {
struct rb_root tlink_tree;
@@ -67,5 +68,6 @@ struct cifs_sb_info {
struct backing_dev_info bdi;
struct delayed_work prune_tlinks;
struct rcu_head rcu;
+ char *prepath;
};
#endif /* _CIFS_FS_SB_H */
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 5d8b7ed..c75d80c 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -649,6 +649,7 @@ cifs_get_root(struct smb_vol *vol, struct super_block *sb)
dentry = child;
} while (!IS_ERR(dentry));
kfree(full_path);
+
return dentry;
}
@@ -688,6 +689,14 @@ cifs_do_mount(struct file_system_type *fs_type,
goto out_cifs_sb;
}
+ if (volume_info->prepath) {
+ cifs_sb->prepath = kstrdup(volume_info->prepath, GFP_KERNEL);
+ if (cifs_sb->prepath == NULL) {
+ root = ERR_PTR(-ENOMEM);
+ goto out_cifs_sb;
+ }
+ }
+
cifs_setup_cifs_sb(volume_info, cifs_sb);
rc = cifs_mount(cifs_sb, volume_info);
@@ -726,7 +735,11 @@ cifs_do_mount(struct file_system_type *fs_type,
sb->s_flags |= MS_ACTIVE;
}
- root = cifs_get_root(volume_info, sb);
+ if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH) {
+ root = dget(sb->s_root);
+ } else {
+ root = cifs_get_root(volume_info, sb);
+ }
if (IS_ERR(root))
goto out_super;
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 66736f5..b82d7b4 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3481,6 +3481,42 @@ cifs_get_volume_info(char *mount_data, const char *devname)
return volume_info;
}
+static int
+cifs_are_all_path_components_accessible(struct TCP_Server_Info *server,
+ unsigned int xid,
+ struct cifs_tcon *tcon,
+ struct cifs_sb_info *cifs_sb,
+ char *full_path)
+{
+ int rc;
+ char *s;
+ char sep, tmp;
+
+ sep = CIFS_DIR_SEP(cifs_sb);
+ s = full_path;
+
+ rc = server->ops->is_path_accessible(xid, tcon, cifs_sb, "");
+ while (rc == 0) {
+ /* skip separators */
+ while (*s == sep)
+ s++;
+ if (!*s)
+ break;
+
+ /* next separator */
+ while (*s && *s != sep)
+ s++;
+
+ /* temporarily null-terminate the path at the end of
+ * the current component */
+ tmp = *s;
+ *s = 0;
+ rc = server->ops->is_path_accessible(xid, tcon, cifs_sb, full_path);
+ *s = tmp;
+ }
+ return rc;
+}
+
int
cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
{
@@ -3618,6 +3654,14 @@ remote_path_check:
kfree(full_path);
goto mount_fail_check;
}
+
+ rc = cifs_are_all_path_components_accessible(server, xid, tcon, cifs_sb, full_path);
+ if (rc != 0) {
+ cifs_dbg(VFS, "cannot query directories between root and final path, "
+ "enabling CIFS_MOUNT_USE_PREFIX_PATH\n");
+ cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH;
+ rc = 0;
+ }
kfree(full_path);
}
@@ -3887,6 +3931,9 @@ cifs_umount(struct cifs_sb_info *cifs_sb)
bdi_destroy(&cifs_sb->bdi);
kfree(cifs_sb->mountdata);
+ if (cifs_sb->prepath) {
+ kfree(cifs_sb->prepath);
+ }
call_rcu(&cifs_sb->rcu, delayed_free);
}
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index c3eb998..5374253 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -84,6 +84,7 @@ build_path_from_dentry(struct dentry *direntry)
struct dentry *temp;
int namelen;
int dfsplen;
+ int pplen = 0;
char *full_path;
char dirsep;
struct cifs_sb_info *cifs_sb = CIFS_SB(direntry->d_sb);
@@ -95,8 +96,12 @@ build_path_from_dentry(struct dentry *direntry)
dfsplen = strnlen(tcon->treeName, MAX_TREE_SIZE + 1);
else
dfsplen = 0;
+
+ if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH)
+ pplen = cifs_sb->prepath ? strlen(cifs_sb->prepath) + 1 : 0;
+
cifs_bp_rename_retry:
- namelen = dfsplen;
+ namelen = dfsplen + pplen;
seq = read_seqbegin(&rename_lock);
rcu_read_lock();
for (temp = direntry; !IS_ROOT(temp);) {
@@ -137,7 +142,7 @@ cifs_bp_rename_retry:
}
}
rcu_read_unlock();
- if (namelen != dfsplen || read_seqretry(&rename_lock, seq)) {
+ if (namelen != dfsplen + pplen || read_seqretry(&rename_lock, seq)) {
cifs_dbg(FYI, "did not end path lookup where expected. namelen=%ddfsplen=%d\n",
namelen, dfsplen);
/* presumably this is only possible if racing with a rename
@@ -153,6 +158,16 @@ cifs_bp_rename_retry:
those safely to '/' if any are found in the middle of the prepath */
/* BB test paths to Windows with '/' in the midst of prepath */
+ if (pplen) {
+ int i;
+ cifs_dbg(FYI, "using cifs_sb prepath <%s>\n", cifs_sb->prepath);
+ memcpy(full_path+dfsplen+1, cifs_sb->prepath, pplen-1);
+ full_path[dfsplen] = '\\';
+ for (i = 0; i < pplen-1; i++)
+ if (full_path[dfsplen+1+i] == '/')
+ full_path[dfsplen+1+i] = CIFS_DIR_SEP(cifs_sb);
+ }
+
if (dfsplen) {
strncpy(full_path, tcon->treeName, dfsplen);
if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) {
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 514dadb..7c6edd7 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -1002,10 +1002,21 @@ struct inode *cifs_root_iget(struct super_block *sb)
struct inode *inode = NULL;
long rc;
struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
+ char *path = NULL;
+ int len;
+
+ if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH) && cifs_sb->prepath) {
+ len = strlen(cifs_sb->prepath);
+ path = kzalloc(len + 2 /* leading sep + null */, GFP_KERNEL);
+ path[0] = '/';
+ memcpy(path+1, cifs_sb->prepath, len);
+ } else {
+ path = kstrdup("", GFP_KERNEL);
+ }
xid = get_xid();
if (tcon->unix_ext) {
- rc = cifs_get_inode_info_unix(&inode, "", sb, xid);
+ rc = cifs_get_inode_info_unix(&inode, path, sb, xid);
/* some servers mistakenly claim POSIX support */
if (rc != -EOPNOTSUPP)
goto iget_no_retry;
@@ -1013,7 +1024,8 @@ struct inode *cifs_root_iget(struct super_block *sb)
tcon->unix_ext = false;
}
- rc = cifs_get_inode_info(&inode, "", NULL, sb, xid, NULL);
+ convert_delimiter(path, CIFS_DIR_SEP(cifs_sb));
+ rc = cifs_get_inode_info(&inode, path, NULL, sb, xid, NULL);
iget_no_retry:
if (!inode) {
@@ -1042,6 +1054,7 @@ iget_no_retry:
}
out:
+ kfree(path);
/* can not call macro free_xid here since in a void func
* TODO: This is no longer true
*/
--
2.1.4
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