From: Davide Ornaghi Date: Mon, 15 Jun 2026 11:35:01 +0000 (+0900) Subject: ksmbd: fix path resolution in ksmbd_vfs_kern_path_create X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=1c8951963d8ed357f70f59e0ad4ddce2199d2016;p=thirdparty%2Flinux.git ksmbd: fix path resolution in ksmbd_vfs_kern_path_create The SMB2 open lookup is rooted at the share with LOOKUP_BENEATH, but the create/mkdir/hardlink sink is not: ksmbd_vfs_kern_path_create() builds an absolute path with convert_to_unix_name() and resolves it from AT_FDCWD via start_creating_path(), so a ".." component is walked from the real filesystem root and escapes the export. An authenticated client races a missing path component so the rooted open lookup returns -ENOENT (taking the create branch) while the same component is present (a directory) when the create walk runs; the create then resolves ".." out of the share. Root the create walk at the share like the lookup and rename paths already are: resolve the parent with vfs_path_parent_lookup(..., LOOKUP_BENEATH, &share_conf->vfs_path) and create the final component with start_creating_noperm(). convert_to_unix_name() then has no callers and is removed. Fixes: 265fd1991c1d ("ksmbd: use LOOKUP_BENEATH to prevent the out of share access") Cc: stable@vger.kernel.org Signed-off-by: Davide Ornaghi Acked-by: Namjae Jeon Signed-off-by: Steve French --- diff --git a/fs/smb/server/misc.c b/fs/smb/server/misc.c index a543ec9d35817..966004c414a8c 100644 --- a/fs/smb/server/misc.c +++ b/fs/smb/server/misc.c @@ -283,39 +283,6 @@ char *ksmbd_extract_sharename(struct unicode_map *um, const char *treename) return ksmbd_casefold_sharename(um, name); } -/** - * convert_to_unix_name() - convert windows name to unix format - * @share: ksmbd_share_config pointer - * @name: file name that is relative to share - * - * Return: converted name on success, otherwise NULL - */ -char *convert_to_unix_name(struct ksmbd_share_config *share, const char *name) -{ - int no_slash = 0, name_len, path_len; - char *new_name; - - if (name[0] == '/') - name++; - - path_len = share->path_sz; - name_len = strlen(name); - new_name = kmalloc(path_len + name_len + 2, KSMBD_DEFAULT_GFP); - if (!new_name) - return new_name; - - memcpy(new_name, share->path, path_len); - if (new_name[path_len - 1] != '/') { - new_name[path_len] = '/'; - no_slash = 1; - } - - memcpy(new_name + path_len + no_slash, name, name_len); - path_len += name_len + no_slash; - new_name[path_len] = 0x00; - return new_name; -} - char *ksmbd_convert_dir_info_name(struct ksmbd_dir_info *d_info, const struct nls_table *local_nls, int *conv_len) diff --git a/fs/smb/server/misc.h b/fs/smb/server/misc.h index 13423696ae8c6..3909104e18ad4 100644 --- a/fs/smb/server/misc.h +++ b/fs/smb/server/misc.h @@ -25,7 +25,6 @@ void ksmbd_strip_last_slash(char *path); void ksmbd_conv_path_to_windows(char *path); char *ksmbd_casefold_sharename(struct unicode_map *um, const char *name); char *ksmbd_extract_sharename(struct unicode_map *um, const char *treename); -char *convert_to_unix_name(struct ksmbd_share_config *share, const char *name); #define KSMBD_DIR_INFO_ALIGNMENT 8 struct ksmbd_dir_info; diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c index fe376453a5198..74b0307cb1009 100644 --- a/fs/smb/server/vfs.c +++ b/fs/smb/server/vfs.c @@ -1259,15 +1259,30 @@ struct dentry *ksmbd_vfs_kern_path_create(struct ksmbd_work *work, unsigned int flags, struct path *path) { - char *abs_name; + struct ksmbd_share_config *share_conf = work->tcon->share_conf; + struct qstr last; struct dentry *dent; + int err; - abs_name = convert_to_unix_name(work->tcon->share_conf, name); - if (!abs_name) - return ERR_PTR(-ENOMEM); + /* resolve the name beneath the share root so ".." cannot escape */ + CLASS(filename_kernel, filename)(name); - dent = start_creating_path(AT_FDCWD, abs_name, path, flags); - kfree(abs_name); + err = vfs_path_parent_lookup(filename, flags | LOOKUP_BENEATH, + path, &last, &share_conf->vfs_path); + if (err) + return ERR_PTR(err); + + err = mnt_want_write(path->mnt); + if (err) { + path_put(path); + return ERR_PTR(err); + } + + dent = start_creating_noperm(path->dentry, &last); + if (IS_ERR(dent)) { + mnt_drop_write(path->mnt); + path_put(path); + } return dent; }