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ksmbd: remove follow symlinks support
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Use  LOOKUP_NO_SYMLINKS flags for default lookup to prohibit the middle of
symlink component lookup and remove follow symlinks parameter support.
We re-implement it as reparse point later.

Test result:
smbclient -Ulinkinjeon%1234 //172.30.1.42/share -c
"get hacked/passwd passwd"
NT_STATUS_OBJECT_NAME_NOT_FOUND opening remote file \hacked\passwd

Cc: Ralph Böhme <slow@samba.org>
Cc: Steve French <smfrench@gmail.com>
Acked-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
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Namjae Jeon authored and Steve French committed Sep 23, 2021
1 parent 18a015b commit 4ea4779
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Showing 2 changed files with 19 additions and 56 deletions.
43 changes: 10 additions & 33 deletions fs/ksmbd/smb2pdu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2632,13 +2632,9 @@ int smb2_open(struct ksmbd_work *work)
goto err_out1;
}

if (req->CreateOptions & FILE_DELETE_ON_CLOSE_LE) {
/*
* On delete request, instead of following up, need to
* look the current entity
*/
rc = ksmbd_vfs_kern_path(name, 0, &path, 1);
if (!rc) {
rc = ksmbd_vfs_kern_path(name, LOOKUP_NO_SYMLINKS, &path, 1);
if (!rc) {
if (req->CreateOptions & FILE_DELETE_ON_CLOSE_LE) {
/*
* If file exists with under flags, return access
* denied error.
Expand All @@ -2657,25 +2653,10 @@ int smb2_open(struct ksmbd_work *work)
path_put(&path);
goto err_out;
}
}
} else {
if (test_share_config_flag(work->tcon->share_conf,
KSMBD_SHARE_FLAG_FOLLOW_SYMLINKS)) {
/*
* Use LOOKUP_FOLLOW to follow the path of
* symlink in path buildup
*/
rc = ksmbd_vfs_kern_path(name, LOOKUP_FOLLOW, &path, 1);
if (rc) { /* Case for broken link ?*/
rc = ksmbd_vfs_kern_path(name, 0, &path, 1);
}
} else {
rc = ksmbd_vfs_kern_path(name, 0, &path, 1);
if (!rc && d_is_symlink(path.dentry)) {
rc = -EACCES;
path_put(&path);
goto err_out;
}
} else if (d_is_symlink(path.dentry)) {
rc = -EACCES;
path_put(&path);
goto err_out;
}
}

Expand Down Expand Up @@ -4751,12 +4732,8 @@ static int smb2_get_info_filesystem(struct ksmbd_work *work,
struct path path;
int rc = 0, len;
int fs_infoclass_size = 0;
int lookup_flags = 0;

if (test_share_config_flag(share, KSMBD_SHARE_FLAG_FOLLOW_SYMLINKS))
lookup_flags = LOOKUP_FOLLOW;

rc = ksmbd_vfs_kern_path(share->path, lookup_flags, &path, 0);
rc = ksmbd_vfs_kern_path(share->path, LOOKUP_NO_SYMLINKS, &path, 0);
if (rc) {
pr_err("cannot create vfs path\n");
return -EIO;
Expand Down Expand Up @@ -5333,7 +5310,7 @@ static int smb2_rename(struct ksmbd_work *work,
}

ksmbd_debug(SMB, "new name %s\n", new_name);
rc = ksmbd_vfs_kern_path(new_name, 0, &path, 1);
rc = ksmbd_vfs_kern_path(new_name, LOOKUP_NO_SYMLINKS, &path, 1);
if (rc)
file_present = false;
else
Expand Down Expand Up @@ -5407,7 +5384,7 @@ static int smb2_create_link(struct ksmbd_work *work,
}

ksmbd_debug(SMB, "target name is %s\n", target_name);
rc = ksmbd_vfs_kern_path(link_name, 0, &path, 0);
rc = ksmbd_vfs_kern_path(link_name, LOOKUP_NO_SYMLINKS, &path, 0);
if (rc)
file_present = false;
else
Expand Down
32 changes: 9 additions & 23 deletions fs/ksmbd/vfs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -166,7 +166,7 @@ int ksmbd_vfs_create(struct ksmbd_work *work, const char *name, umode_t mode)
struct dentry *dentry;
int err;

dentry = kern_path_create(AT_FDCWD, name, &path, 0);
dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_NO_SYMLINKS);
if (IS_ERR(dentry)) {
err = PTR_ERR(dentry);
if (err != -ENOENT)
Expand Down Expand Up @@ -203,7 +203,8 @@ int ksmbd_vfs_mkdir(struct ksmbd_work *work, const char *name, umode_t mode)
struct dentry *dentry;
int err;

dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
dentry = kern_path_create(AT_FDCWD, name, &path,
LOOKUP_NO_SYMLINKS | LOOKUP_DIRECTORY);
if (IS_ERR(dentry)) {
err = PTR_ERR(dentry);
if (err != -EEXIST)
Expand Down Expand Up @@ -588,16 +589,11 @@ int ksmbd_vfs_remove_file(struct ksmbd_work *work, char *name)
struct path path;
struct dentry *parent;
int err;
int flags = 0;

if (ksmbd_override_fsids(work))
return -ENOMEM;

if (test_share_config_flag(work->tcon->share_conf,
KSMBD_SHARE_FLAG_FOLLOW_SYMLINKS))
flags = LOOKUP_FOLLOW;

err = kern_path(name, flags, &path);
err = kern_path(name, LOOKUP_NO_SYMLINKS, &path);
if (err) {
ksmbd_debug(VFS, "can't get %s, err %d\n", name, err);
ksmbd_revert_fsids(work);
Expand Down Expand Up @@ -652,24 +648,19 @@ int ksmbd_vfs_link(struct ksmbd_work *work, const char *oldname,
struct path oldpath, newpath;
struct dentry *dentry;
int err;
int flags = 0;

if (ksmbd_override_fsids(work))
return -ENOMEM;

if (test_share_config_flag(work->tcon->share_conf,
KSMBD_SHARE_FLAG_FOLLOW_SYMLINKS))
flags = LOOKUP_FOLLOW;

err = kern_path(oldname, flags, &oldpath);
err = kern_path(oldname, LOOKUP_NO_SYMLINKS, &oldpath);
if (err) {
pr_err("cannot get linux path for %s, err = %d\n",
oldname, err);
goto out1;
}

dentry = kern_path_create(AT_FDCWD, newname, &newpath,
flags | LOOKUP_REVAL);
LOOKUP_NO_SYMLINKS | LOOKUP_REVAL);
if (IS_ERR(dentry)) {
err = PTR_ERR(dentry);
pr_err("path create err for %s, err %d\n", newname, err);
Expand Down Expand Up @@ -788,7 +779,6 @@ int ksmbd_vfs_fp_rename(struct ksmbd_work *work, struct ksmbd_file *fp,
struct dentry *src_dent, *trap_dent, *src_child;
char *dst_name;
int err;
int flags;

dst_name = extract_last_component(newname);
if (!dst_name)
Expand All @@ -797,12 +787,8 @@ int ksmbd_vfs_fp_rename(struct ksmbd_work *work, struct ksmbd_file *fp,
src_dent_parent = dget_parent(fp->filp->f_path.dentry);
src_dent = fp->filp->f_path.dentry;

flags = LOOKUP_DIRECTORY;
if (test_share_config_flag(work->tcon->share_conf,
KSMBD_SHARE_FLAG_FOLLOW_SYMLINKS))
flags |= LOOKUP_FOLLOW;

err = kern_path(newname, flags, &dst_path);
err = kern_path(newname, LOOKUP_NO_SYMLINKS | LOOKUP_DIRECTORY,
&dst_path);
if (err) {
ksmbd_debug(VFS, "Cannot get path for %s [%d]\n", newname, err);
goto out;
Expand Down Expand Up @@ -861,7 +847,7 @@ int ksmbd_vfs_truncate(struct ksmbd_work *work, const char *name,
int err = 0;

if (name) {
err = kern_path(name, 0, &path);
err = kern_path(name, LOOKUP_NO_SYMLINKS, &path);
if (err) {
pr_err("cannot get linux path for %s, err %d\n",
name, err);
Expand Down

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