From 95c5d0607a54f02551bdd9ecc7f41b1d35b19211 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Sat, 27 Feb 2021 02:01:46 -0600
Subject: [PATCH] smb3: allow files to be created with backslash in name

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@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
 fs/cifs/cifs_unicode.c | 15 ++++++++++-----
 fs/cifs/cifs_unicode.h |  3 +++
 fs/cifs/cifsglob.h     |  5 +----
 fs/cifs/dir.c          | 18 ++++++++++++------
 fs/cifs/misc.c         |  2 +-
 fs/cifs/smb2misc.c     | 18 +++++++++++-------
 6 files changed, 38 insertions(+), 23 deletions(-)

diff --git a/fs/cifs/cifs_unicode.c b/fs/cifs/cifs_unicode.c
index 9bd03a231032..4898b1553796 100644
--- a/fs/cifs/cifs_unicode.c
+++ b/fs/cifs/cifs_unicode.c
@@ -98,6 +98,9 @@ convert_sfm_char(const __u16 src_char, char *target)
 	case SFM_PERIOD:
 		*target = '.';
 		break;
+	case SFM_SLASH:
+		*target = '\\';
+		break;
 	default:
 		return false;
 	}
@@ -431,6 +434,9 @@ static __le16 convert_to_sfm_char(char src_char, bool end_of_string)
 	case '|':
 		dest_char = cpu_to_le16(SFM_PIPE);
 		break;
+	case '\\':
+		dest_char = cpu_to_le16(SFM_SLASH);
+		break;
 	case '.':
 		if (end_of_string)
 			dest_char = cpu_to_le16(SFM_PERIOD);
@@ -443,6 +449,9 @@ static __le16 convert_to_sfm_char(char src_char, bool end_of_string)
 		else
 			dest_char = 0;
 		break;
+	case '/':
+		dest_char = cpu_to_le16(UCS2_SLASH);
+		break;
 	default:
 		dest_char = 0;
 	}
@@ -502,11 +511,7 @@ cifsConvertToUTF16(__le16 *target, const char *source, int srclen,
 			dst_char = convert_to_sfm_char(src_char, end_of_string);
 		} else
 			dst_char = 0;
-		/*
-		 * FIXME: We can not handle remapping backslash (UNI_SLASH)
-		 * until all the calls to build_path_from_dentry are modified,
-		 * as they use backslash as separator.
-		 */
+
 		if (dst_char == 0) {
 			charlen = cp->char2uni(source + i, srclen - i, &tmp);
 			dst_char = cpu_to_le16(tmp);
diff --git a/fs/cifs/cifs_unicode.h b/fs/cifs/cifs_unicode.h
index 80b3d845419f..8cd58c71cbb6 100644
--- a/fs/cifs/cifs_unicode.h
+++ b/fs/cifs/cifs_unicode.h
@@ -24,6 +24,9 @@
 
 #define  UNIUPR_NOLOWER		/* Example to not expand lower case tables */
 
+/* Unicode encoding of backslash character */
+#define UCS2_SLASH 0x005C
+
 /*
  * Windows maps these to the user defined 16 bit Unicode range since they are
  * reserved symbols (along with \ and /), otherwise illegal to store
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 3de3c5908a72..95bd980ec849 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1430,10 +1430,7 @@ 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 '/';
 }
 
 static inline void
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 97ac363b5df1..bba0fa1c118b 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -209,12 +209,18 @@ 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))
+		return 0;
+
+	for (i = 0; i < direntry->d_name.len; i++) {
+		if (direntry->d_name.name[i] == '\\') {
+			cifs_dbg(FYI, "Invalid file name\n");
+			return -EINVAL;
 		}
 	}
 	return 0;
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 82e176720ca6..9361644f7310 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -1186,7 +1186,7 @@ int update_super_prepath(struct cifs_tcon *tcon, char *prefix)
 			goto out;
 		}
 
-		convert_delimiter(cifs_sb->prepath, CIFS_DIR_SEP(cifs_sb));
+		convert_delimiter(cifs_sb->prepath, CIFS_DIR_SEP(cifs_sb)); /* BB Check this */
 	} else
 		cifs_sb->prepath = NULL;
 
diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c
index 60d4bd1eae2b..ce4f00069653 100644
--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -476,13 +476,17 @@ 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) ||
+		    (cifs_sb_master_tlink(cifs_sb) &&
+		     (cifs_sb_master_tcon(cifs_sb)->posix_extensions)))
+			start_of_path = from + 1;
+	}
 
 	to = cifs_strndup_to_utf16(start_of_path, PATH_MAX, &len,
 				   cifs_sb->local_nls, map_type);
-- 
2.27.0

