Steve French <smfrench@xxxxxxxxx> writes:
> Updated patch (rebased to current for-next-next)
>
> Backslash is reserved in Windows (and SMB2/SMB3 by default) but
> allowed in POSIX so must be remapped when POSIX extensions are
> not enabled.
>
> The default mapping for SMB3 mounts ("SFM") allows mapping backslash
> (ie 0x5C in UTF8) to 0xF026 in UCS-2 (using the Unicode remapping
> range reserved for these characters), but this was not mapped by
> cifs.ko (unlike asterisk, greater than, question mark etc). This patch
> fixes that to allow creating files and directories with backslash
> in the file or directory name.
>
> Before this patch:
> touch "/mnt2/filewith\slash"
> would return
> touch: setting times of '/mnt2/filewith\slash': Invalid argument
>
> With the patch touch and mkdir with the backslash in the name works.
>
> This problem was found while debugging xfstest generic/453
> https://bugzilla.kernel.org/show_bug.cgi?id=210961
>
> Reported-by: Xiaoli Feng <xifeng@xxxxxxxxxx>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=210961
> Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
>
>
> @Paulo Alcantara any thoughts if additional changes needed for DFS or
> prefixpaths?
Yes - these changes break DFS mounts with iocharsets different than
utf8. Consider dfs_cache_canonical_path() where the backslashes will
get remapped in cifs_strndup_to_utf16() and then broken DFS referral
paths will be sent over the wire.
You can simply reproduce this with
mount.cifs //srv/dfs /mnt -o ...,iocharset=ascii
> diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
> index 55b3ce944022..e6f4a28275a8 100644
> --- a/fs/smb/client/cifsglob.h
> +++ b/fs/smb/client/cifsglob.h
> @@ -1568,10 +1568,7 @@ CIFS_FILE_SB(struct file *file)
>
> static inline char CIFS_DIR_SEP(const struct cifs_sb_info *cifs_sb)
> {
> - if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS)
> - return '/';
> - else
> - return '\\';
> + return '/';
> }
This change breakes readdir(2) under SMB1 mounts (no UNIX extensions)
because CIFSFindFirst() ends up appending "/*" rather than "\\*" to
filename and then fails with STATUS_OBJECT_NAME_INVALID.
You'd need to check all other places where we could also append an UTF16
string with CIFS_DIR_SEP() after getting the path with
cifs_convert_path_to_utf16().
> diff --git a/fs/smb/client/dir.c b/fs/smb/client/dir.c
> index 580a27a3a7e6..6c446b1210ba 100644
> --- a/fs/smb/client/dir.c
> +++ b/fs/smb/client/dir.c
> @@ -160,12 +160,18 @@ check_name(struct dentry *direntry, struct cifs_tcon *tcon)
> le32_to_cpu(tcon->fsAttrInfo.MaxPathNameComponentLength)))
> return -ENAMETOOLONG;
>
> - if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS)) {
> - for (i = 0; i < direntry->d_name.len; i++) {
> - if (direntry->d_name.name[i] == '\\') {
> - cifs_dbg(FYI, "Invalid file name\n");
> - return -EINVAL;
> - }
> + /*
> + * SMB3.1.1 POSIX Extensions, CIFS Unix Extensions and SFM mappings
> + * allow \ in paths (or in latter case remaps \ to 0xF026)
> + */
> + if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) ||
> + (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SFM_CHR))
What about
if (cifs_sb->mnt_cifs_flags & (CIFS_MOUNT_POSIX_PATHS | CIFS_MOUNT_MAP_SFM_CHR))
> diff --git a/fs/smb/client/smb2misc.c b/fs/smb/client/smb2misc.c
> index e20b4354e703..0edc888ec3f8 100644
> --- a/fs/smb/client/smb2misc.c
> +++ b/fs/smb/client/smb2misc.c
> @@ -469,13 +469,17 @@ cifs_convert_path_to_utf16(const char *from, struct cifs_sb_info *cifs_sb)
> if (from[0] == '\\')
> start_of_path = from + 1;
>
> - /* SMB311 POSIX extensions paths do not include leading slash */
> - else if (cifs_sb_master_tlink(cifs_sb) &&
> - cifs_sb_master_tcon(cifs_sb)->posix_extensions &&
> - (from[0] == '/')) {
> - start_of_path = from + 1;
> - } else
> - start_of_path = from;
> + start_of_path = from;
> + /*
> + * Only old CIFS Unix extensions paths include leading slash
> + * Need to skip if for SMB3.1.1 POSIX Extensions and SMB1/2/3
> + */
> + if (from[0] == '/') {
> + if (((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) == false) ||
I guess you meant "== 0". Also, no need for extra parentheses.
