From 3eb40512530e4f64f819d8e723b6f41695dace5a Mon Sep 17 00:00:00 2001 From: Pali Rohár Date: Sat, 5 Oct 2024 16:02:55 +0200 Subject: cifs: Improve creating native symlinks pointing to directory MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit SMB protocol for native symlinks distinguish between symlink to directory and symlink to file. These two symlink types cannot be exchanged, which means that symlink of file type pointing to directory cannot be resolved at all (and vice-versa). Windows follows this rule for local filesystems (NTFS) and also for SMB. Linux SMB client currenly creates all native symlinks of file type. Which means that Windows (and some other SMB clients) cannot resolve symlinks pointing to directory created by Linux SMB client. As Linux system does not distinguish between directory and file symlinks, its API does not provide enough information for Linux SMB client during creating of native symlinks. Add some heuristic into the Linux SMB client for choosing the correct symlink type during symlink creation. Check if the symlink target location ends with slash, or last path component is dot or dot-dot, and check if the target location on SMB share exists and is a directory. If at least one condition is truth then create a new SMB symlink of directory type. Otherwise create it as file type symlink. This change improves interoperability with Windows systems. Windows systems would be able to resolve more SMB symlinks created by Linux SMB client which points to existing directory. Signed-off-by: Pali Rohár Signed-off-by: Steve French --- fs/smb/client/reparse.c | 164 +++++++++++++++++++++++++++++++++++++++++++++- fs/smb/client/smb2inode.c | 3 +- fs/smb/client/smb2proto.h | 1 + 3 files changed, 164 insertions(+), 4 deletions(-) diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c index c848b5e88d32..74abbdf5026c 100644 --- a/fs/smb/client/reparse.c +++ b/fs/smb/client/reparse.c @@ -14,6 +14,12 @@ #include "fs_context.h" #include "reparse.h" +static int detect_directory_symlink_target(struct cifs_sb_info *cifs_sb, + const unsigned int xid, + const char *full_path, + const char *symname, + bool *directory); + int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode, struct dentry *dentry, struct cifs_tcon *tcon, const char *full_path, const char *symname) @@ -24,6 +30,7 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode, struct inode *new; struct kvec iov; __le16 *path; + bool directory; char *sym, sep = CIFS_DIR_SEP(cifs_sb); u16 len, plen; int rc = 0; @@ -45,6 +52,18 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode, goto out; } + /* + * SMB distinguish between symlink to directory and symlink to file. + * They cannot be exchanged (symlink of file type which points to + * directory cannot be resolved and vice-versa). Try to detect if + * the symlink target could be a directory or not. When detection + * fails then treat symlink as a file (non-directory) symlink. + */ + directory = false; + rc = detect_directory_symlink_target(cifs_sb, xid, full_path, symname, &directory); + if (rc < 0) + goto out; + plen = 2 * UniStrnlen((wchar_t *)path, PATH_MAX); len = sizeof(*buf) + plen * 2; buf = kzalloc(len, GFP_KERNEL); @@ -69,7 +88,8 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode, iov.iov_base = buf; iov.iov_len = len; new = smb2_get_reparse_inode(&data, inode->i_sb, xid, - tcon, full_path, &iov, NULL); + tcon, full_path, directory, + &iov, NULL); if (!IS_ERR(new)) d_instantiate(dentry, new); else @@ -81,6 +101,144 @@ out: return rc; } +static int detect_directory_symlink_target(struct cifs_sb_info *cifs_sb, + const unsigned int xid, + const char *full_path, + const char *symname, + bool *directory) +{ + char sep = CIFS_DIR_SEP(cifs_sb); + struct cifs_open_parms oparms; + struct tcon_link *tlink; + struct cifs_tcon *tcon; + const char *basename; + struct cifs_fid fid; + char *resolved_path; + int full_path_len; + int basename_len; + int symname_len; + char *path_sep; + __u32 oplock; + int open_rc; + + /* + * First do some simple check. If the original Linux symlink target ends + * with slash, or last path component is dot or dot-dot then it is for + * sure symlink to the directory. + */ + basename = kbasename(symname); + basename_len = strlen(basename); + if (basename_len == 0 || /* symname ends with slash */ + (basename_len == 1 && basename[0] == '.') || /* last component is "." */ + (basename_len == 2 && basename[0] == '.' && basename[1] == '.')) { /* or ".." */ + *directory = true; + return 0; + } + + /* + * For absolute symlinks it is not possible to determinate + * if it should point to directory or file. + */ + if (symname[0] == '/') { + cifs_dbg(FYI, + "%s: cannot determinate if the symlink target path '%s' " + "is directory or not, creating '%s' as file symlink\n", + __func__, symname, full_path); + return 0; + } + + /* + * If it was not detected as directory yet and the symlink is relative + * then try to resolve the path on the SMB server, check if the path + * exists and determinate if it is a directory or not. + */ + + full_path_len = strlen(full_path); + symname_len = strlen(symname); + + tlink = cifs_sb_tlink(cifs_sb); + if (IS_ERR(tlink)) + return PTR_ERR(tlink); + + resolved_path = kzalloc(full_path_len + symname_len + 1, GFP_KERNEL); + if (!resolved_path) { + cifs_put_tlink(tlink); + return -ENOMEM; + } + + /* + * Compose the resolved SMB symlink path from the SMB full path + * and Linux target symlink path. + */ + memcpy(resolved_path, full_path, full_path_len+1); + path_sep = strrchr(resolved_path, sep); + if (path_sep) + path_sep++; + else + path_sep = resolved_path; + memcpy(path_sep, symname, symname_len+1); + if (sep == '\\') + convert_delimiter(path_sep, sep); + + tcon = tlink_tcon(tlink); + oparms = CIFS_OPARMS(cifs_sb, tcon, resolved_path, + FILE_READ_ATTRIBUTES, FILE_OPEN, 0, ACL_NO_MODE); + oparms.fid = &fid; + + /* Try to open as a directory (NOT_FILE) */ + oplock = 0; + oparms.create_options = cifs_create_options(cifs_sb, + CREATE_NOT_FILE | OPEN_REPARSE_POINT); + open_rc = tcon->ses->server->ops->open(xid, &oparms, &oplock, NULL); + if (open_rc == 0) { + /* Successful open means that the target path is definitely a directory. */ + *directory = true; + tcon->ses->server->ops->close(xid, tcon, &fid); + } else if (open_rc == -ENOTDIR) { + /* -ENOTDIR means that the target path is definitely a file. */ + *directory = false; + } else if (open_rc == -ENOENT) { + /* -ENOENT means that the target path does not exist. */ + cifs_dbg(FYI, + "%s: symlink target path '%s' does not exist, " + "creating '%s' as file symlink\n", + __func__, symname, full_path); + } else { + /* Try to open as a file (NOT_DIR) */ + oplock = 0; + oparms.create_options = cifs_create_options(cifs_sb, + CREATE_NOT_DIR | OPEN_REPARSE_POINT); + open_rc = tcon->ses->server->ops->open(xid, &oparms, &oplock, NULL); + if (open_rc == 0) { + /* Successful open means that the target path is definitely a file. */ + *directory = false; + tcon->ses->server->ops->close(xid, tcon, &fid); + } else if (open_rc == -EISDIR) { + /* -EISDIR means that the target path is definitely a directory. */ + *directory = true; + } else { + /* + * This code branch is called when we do not have a permission to + * open the resolved_path or some other client/process denied + * opening the resolved_path. + * + * TODO: Try to use ops->query_dir_first on the parent directory + * of resolved_path, search for basename of resolved_path and + * check if the ATTR_DIRECTORY is set in fi.Attributes. In some + * case this could work also when opening of the path is denied. + */ + cifs_dbg(FYI, + "%s: cannot determinate if the symlink target path '%s' " + "is directory or not, creating '%s' as file symlink\n", + __func__, symname, full_path); + } + } + + kfree(resolved_path); + cifs_put_tlink(tlink); + return 0; +} + static int nfs_set_reparse_buf(struct reparse_posix_data *buf, mode_t mode, dev_t dev, struct kvec *iov) @@ -137,7 +295,7 @@ static int mknod_nfs(unsigned int xid, struct inode *inode, }; new = smb2_get_reparse_inode(&data, inode->i_sb, xid, - tcon, full_path, &iov, NULL); + tcon, full_path, false, &iov, NULL); if (!IS_ERR(new)) d_instantiate(dentry, new); else @@ -283,7 +441,7 @@ static int mknod_wsl(unsigned int xid, struct inode *inode, data.wsl.eas_len = len; new = smb2_get_reparse_inode(&data, inode->i_sb, - xid, tcon, full_path, + xid, tcon, full_path, false, &reparse_iov, &xattr_iov); if (!IS_ERR(new)) d_instantiate(dentry, new); diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c index 4e9e225520a6..e49d0c25eb03 100644 --- a/fs/smb/client/smb2inode.c +++ b/fs/smb/client/smb2inode.c @@ -1198,6 +1198,7 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data, const unsigned int xid, struct cifs_tcon *tcon, const char *full_path, + bool directory, struct kvec *reparse_iov, struct kvec *xattr_iov) { @@ -1217,7 +1218,7 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data, FILE_READ_ATTRIBUTES | FILE_WRITE_ATTRIBUTES, FILE_CREATE, - CREATE_NOT_DIR | OPEN_REPARSE_POINT, + (directory ? CREATE_NOT_FILE : CREATE_NOT_DIR) | OPEN_REPARSE_POINT, ACL_NO_MODE); if (xattr_iov) oparms.ea_cctx = xattr_iov; diff --git a/fs/smb/client/smb2proto.h b/fs/smb/client/smb2proto.h index c7e1b149877a..6f9885e4f66c 100644 --- a/fs/smb/client/smb2proto.h +++ b/fs/smb/client/smb2proto.h @@ -61,6 +61,7 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data, const unsigned int xid, struct cifs_tcon *tcon, const char *full_path, + bool directory, struct kvec *reparse_iov, struct kvec *xattr_iov); int smb2_query_reparse_point(const unsigned int xid, -- cgit v1.2.3-70-g09d2 From 63271b7d569fbe924bccc7dadc17d3d07a4e5f7a Mon Sep 17 00:00:00 2001 From: Pali Rohár Date: Sat, 5 Oct 2024 16:02:56 +0200 Subject: cifs: Fix creating native symlinks pointing to current or parent directory MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Calling 'ln -s . symlink' or 'ln -s .. symlink' creates symlink pointing to some object name which ends with U+F029 unicode codepoint. This is because trailing dot in the object name is replaced by non-ASCII unicode codepoint. So Linux SMB client currently is not able to create native symlink pointing to current or parent directory on Windows SMB server which can be read by either on local Windows server or by any other SMB client which does not implement compatible-reverse character replacement. Fix this problem in cifsConvertToUTF16() function which is doing that character replacement. Function comment already says that it does not need to handle special cases '.' and '..', but after introduction of native symlinks in reparse point form, this handling is needed. Note that this change depends on the previous change "cifs: Improve creating native symlinks pointing to directory". Signed-off-by: Pali Rohár Signed-off-by: Steve French --- fs/smb/client/cifs_unicode.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/fs/smb/client/cifs_unicode.c b/fs/smb/client/cifs_unicode.c index 79d99a913944..4cc6e0896fad 100644 --- a/fs/smb/client/cifs_unicode.c +++ b/fs/smb/client/cifs_unicode.c @@ -484,10 +484,21 @@ cifsConvertToUTF16(__le16 *target, const char *source, int srclen, /** * Remap spaces and periods found at the end of every * component of the path. The special cases of '.' and - * '..' do not need to be dealt with explicitly because - * they are addressed in namei.c:link_path_walk(). + * '..' are need to be handled because of symlinks. + * They are treated as non-end-of-string to avoid + * remapping and breaking symlinks pointing to . or .. **/ - if ((i == srclen - 1) || (source[i+1] == '\\')) + if ((i == 0 || source[i-1] == '\\') && + source[i] == '.' && + (i == srclen-1 || source[i+1] == '\\')) + end_of_string = false; /* "." case */ + else if (i >= 1 && + (i == 1 || source[i-2] == '\\') && + source[i-1] == '.' && + source[i] == '.' && + (i == srclen-1 || source[i+1] == '\\')) + end_of_string = false; /* ".." case */ + else if ((i == srclen - 1) || (source[i+1] == '\\')) end_of_string = true; else end_of_string = false; -- cgit v1.2.3-70-g09d2