SMB1 protocol supports non-UNICODE (8-bit OEM character set) and
UNICODE (UTF-16) modes.

Linux SMB1 client implements both of them but currently does not allow to
choose non-UNICODE mode when SMB1 server announce UNICODE mode support.

This change adds a new mount option -o nounicode to disable UNICODE mode
and force usage of non-UNICODE (8-bit OEM character set) mode.

This allows to test non-UNICODE implementation of Linux SMB1 client against
any SMB1 server, including modern and recent Windows SMB1 server.

Signed-off-by: Pali Rohár <pali@kernel.org>
---
 fs/smb/client/cifsfs.c     |  4 ++++
 fs/smb/client/cifsglob.h   |  2 ++
 fs/smb/client/cifssmb.c    |  5 ++++-
 fs/smb/client/connect.c    | 32 +++++++++++++++++++++++++++++---
 fs/smb/client/fs_context.c | 11 +++++++++++
 fs/smb/client/fs_context.h |  2 ++
 fs/smb/client/sess.c       |  1 +
 fs/smb/client/smb1ops.c    |  1 +
 8 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index 1decf91d3f61..447ed7831f2c 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -611,6 +611,10 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
 					   cifs_sb->ctx->dir_mode);
 	if (cifs_sb->ctx->iocharset)
 		seq_printf(s, ",iocharset=%s", cifs_sb->ctx->iocharset);
+	if (tcon->ses->unicode == 0)
+		seq_puts(s, ",nounicode");
+	else if (tcon->ses->unicode == 1)
+		seq_puts(s, ",unicode");
 	if (tcon->seal)
 		seq_puts(s, ",seal");
 	else if (tcon->ses->server->ignore_signature)
diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index dcee43889358..2f77b558abe8 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -651,6 +651,7 @@ struct smb_version_values {
 	unsigned int	cap_unix;
 	unsigned int	cap_nt_find;
 	unsigned int	cap_large_files;
+	unsigned int	cap_unicode;
 	__u16		signing_enabled;
 	__u16		signing_required;
 	size_t		create_lease_size;
@@ -1124,6 +1125,7 @@ struct cifs_ses {
 	bool sign;		/* is signing required? */
 	bool domainAuto:1;
 	bool expired_pwd;  /* track if access denied or expired pwd so can know if need to update */
+	int unicode;
 	unsigned int flags;
 	__u16 session_flags;
 	__u8 smb3signingkey[SMB3_SIGN_KEY_SIZE];
diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
index c6f15dbe860a..6218b59b9da7 100644
--- a/fs/smb/client/cifssmb.c
+++ b/fs/smb/client/cifssmb.c
@@ -423,7 +423,10 @@ CIFSSMBNegotiate(const unsigned int xid,
 		return rc;
 
 	pSMB->hdr.Mid = get_next_mid(server);
-	pSMB->hdr.Flags2 |= (SMBFLG2_UNICODE | SMBFLG2_ERR_STATUS);
+	pSMB->hdr.Flags2 |= SMBFLG2_ERR_STATUS;
+
+	if (ses->unicode != 0)
+		pSMB->hdr.Flags2 |= SMBFLG2_UNICODE;
 
 	if (should_set_ext_sec_flag(ses->sectype)) {
 		cifs_dbg(FYI, "Requesting extended security\n");
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index 612816ec71f5..3d9d736b6e58 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -2338,6 +2338,7 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 	ses->cred_uid = ctx->cred_uid;
 	ses->linux_uid = ctx->linux_uid;
 
+	ses->unicode = ctx->unicode;
 	ses->sectype = ctx->sectype;
 	ses->sign = ctx->sign;
 	ses->local_nls = load_nls(ctx->local_nls->charset);
@@ -3928,7 +3929,7 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 		   struct TCP_Server_Info *server,
 		   struct nls_table *nls_info)
 {
-	int rc = -ENOSYS;
+	int rc = 0;
 	struct TCP_Server_Info *pserver = SERVER_IS_CHAN(server) ? server->primary_server : server;
 	struct sockaddr_in6 *addr6 = (struct sockaddr_in6 *)&pserver->dstaddr;
 	struct sockaddr_in *addr = (struct sockaddr_in *)&pserver->dstaddr;
@@ -3980,6 +3981,26 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 		if (!linuxExtEnabled)
 			ses->capabilities &= (~server->vals->cap_unix);
 
+		/*
+		 * Check if the server supports specified encoding mode.
+		 * Zero value in vals->cap_unicode indidcates that chosen
+		 * protocol dialect does not support non-UNICODE mode.
+		 */
+		if (ses->unicode == 1 && server->vals->cap_unicode != 0 &&
+		    !(server->capabilities & server->vals->cap_unicode)) {
+			cifs_dbg(VFS, "Server does not support mounting in UNICODE mode\n");
+			rc = -EOPNOTSUPP;
+		} else if (ses->unicode == 0 && server->vals->cap_unicode == 0) {
+			cifs_dbg(VFS, "Server does not support mounting in non-UNICODE mode\n");
+			rc = -EOPNOTSUPP;
+		} else if (ses->unicode == 0) {
+			/*
+			 * When UNICODE mode was explicitly disabled then
+			 * do not announce client UNICODE capability.
+			 */
+			ses->capabilities &= (~server->vals->cap_unicode);
+		}
+
 		if (ses->auth_key.response) {
 			cifs_dbg(FYI, "Free previous auth_key.response = %p\n",
 				 ses->auth_key.response);
@@ -3992,8 +4013,12 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
 	cifs_dbg(FYI, "Security Mode: 0x%x Capabilities: 0x%x TimeAdjust: %d\n",
 		 server->sec_mode, server->capabilities, server->timeAdj);
 
-	if (server->ops->sess_setup)
-		rc = server->ops->sess_setup(xid, ses, server, nls_info);
+	if (!rc) {
+		if (server->ops->sess_setup)
+			rc = server->ops->sess_setup(xid, ses, server, nls_info);
+		else
+			rc = -ENOSYS;
+	}
 
 	if (rc) {
 		cifs_server_dbg(VFS, "Send error in SessSetup = %d\n", rc);
@@ -4063,6 +4088,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 	ctx->seal = master_tcon->seal;
 	ctx->witness = master_tcon->use_witness;
 	ctx->dfs_root_ses = master_tcon->ses->dfs_root_ses;
+	ctx->unicode = master_tcon->ses->unicode;
 
 	rc = cifs_set_vol_auth(ctx, master_tcon->ses);
 	if (rc) {
diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index 7dd46cfc9fb3..d970b66e529c 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -127,6 +127,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = {
 	fsparam_flag("rootfs", Opt_rootfs),
 	fsparam_flag("compress", Opt_compress),
 	fsparam_flag("witness", Opt_witness),
+	fsparam_flag_no("unicode", Opt_unicode),
 
 	/* Mount options which take uid or gid */
 	fsparam_uid("backupuid", Opt_backupuid),
@@ -930,6 +931,10 @@ static int smb3_verify_reconfigure_ctx(struct fs_context *fc,
 		cifs_errorf(fc, "can not change iocharset during remount\n");
 		return -EINVAL;
 	}
+	if (new_ctx->unicode != old_ctx->unicode) {
+		cifs_errorf(fc, "can not change unicode during remount\n");
+		return -EINVAL;
+	}
 
 	return 0;
 }
@@ -1520,6 +1525,10 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 		ctx->witness = true;
 		pr_warn_once("Witness protocol support is experimental\n");
 		break;
+	case Opt_unicode:
+		ctx->unicode = !result.negated;
+		cifs_dbg(FYI, "unicode set to %d\n", ctx->unicode);
+		break;
 	case Opt_rootfs:
 #ifndef CONFIG_CIFS_ROOT
 		cifs_dbg(VFS, "rootfs support requires CONFIG_CIFS_ROOT config option\n");
@@ -1816,6 +1825,8 @@ int smb3_init_fs_context(struct fs_context *fc)
 	ctx->symlink_type = CIFS_SYMLINK_TYPE_DEFAULT;
 	ctx->nonativesocket = 0;
 
+	ctx->unicode = -1; /* autodetect, but prefer UNICODE mode */
+
 /*
  *	short int override_uid = -1;
  *	short int override_gid = -1;
diff --git a/fs/smb/client/fs_context.h b/fs/smb/client/fs_context.h
index 18d39d457145..1514e05e6629 100644
--- a/fs/smb/client/fs_context.h
+++ b/fs/smb/client/fs_context.h
@@ -127,6 +127,7 @@ enum cifs_param {
 	Opt_multichannel,
 	Opt_compress,
 	Opt_witness,
+	Opt_unicode,
 
 	/* Mount options which take numeric value */
 	Opt_backupuid,
@@ -296,6 +297,7 @@ struct smb3_fs_context {
 	bool compress; /* enable SMB2 messages (READ/WRITE) de/compression */
 	bool rootfs:1; /* if it's a SMB root file system */
 	bool witness:1; /* use witness protocol */
+	int unicode;
 	char *leaf_fullpath;
 	struct cifs_ses *dfs_root_ses;
 	bool dfs_automount:1; /* set for dfs automount only */
diff --git a/fs/smb/client/sess.c b/fs/smb/client/sess.c
index c88e9657f47a..6a92db287843 100644
--- a/fs/smb/client/sess.c
+++ b/fs/smb/client/sess.c
@@ -529,6 +529,7 @@ cifs_ses_add_channel(struct cifs_ses *ses,
 	ctx->password = ses->password;
 	ctx->sectype = ses->sectype;
 	ctx->sign = ses->sign;
+	ctx->unicode = ses->unicode;
 
 	/* UNC and paths */
 	/* XXX: Use ses->server->hostname? */
diff --git a/fs/smb/client/smb1ops.c b/fs/smb/client/smb1ops.c
index abca214f923c..b0fb4a5c586d 100644
--- a/fs/smb/client/smb1ops.c
+++ b/fs/smb/client/smb1ops.c
@@ -1189,6 +1189,7 @@ struct smb_version_values smb1_values = {
 	.cap_unix = CAP_UNIX,
 	.cap_nt_find = CAP_NT_SMBS | CAP_NT_FIND,
 	.cap_large_files = CAP_LARGE_FILES,
+	.cap_unicode = CAP_UNICODE,
 	.signing_enabled = SECMODE_SIGN_ENABLED,
 	.signing_required = SECMODE_SIGN_REQUIRED,
 };
-- 
2.20.1

you can  simply use iocharset=iso8859-1 mount option if you want to get legacy
charsets on the client side to work. I don't think that it's a good idea to
mess with the ancient non-unicode flag of SMB.

Björn

On 2024-10-28 at 12:03 +0100 Pali Rohár sent off:
> SMB1 protocol supports non-UNICODE (8-bit OEM character set) and
> UNICODE (UTF-16) modes.
> 
> Linux SMB1 client implements both of them but currently does not allow to
> choose non-UNICODE mode when SMB1 server announce UNICODE mode support.
> 
> This change adds a new mount option -o nounicode to disable UNICODE mode
> and force usage of non-UNICODE (8-bit OEM character set) mode.
> 
> This allows to test non-UNICODE implementation of Linux SMB1 client against
> any SMB1 server, including modern and recent Windows SMB1 server.
> 
> Signed-off-by: Pali Rohár <pali@kernel.org>
> ---
>  fs/smb/client/cifsfs.c     |  4 ++++
>  fs/smb/client/cifsglob.h   |  2 ++
>  fs/smb/client/cifssmb.c    |  5 ++++-
>  fs/smb/client/connect.c    | 32 +++++++++++++++++++++++++++++---
>  fs/smb/client/fs_context.c | 11 +++++++++++
>  fs/smb/client/fs_context.h |  2 ++
>  fs/smb/client/sess.c       |  1 +
>  fs/smb/client/smb1ops.c    |  1 +
>  8 files changed, 54 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
> index 1decf91d3f61..447ed7831f2c 100644
> --- a/fs/smb/client/cifsfs.c
> +++ b/fs/smb/client/cifsfs.c
> @@ -611,6 +611,10 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
>  					   cifs_sb->ctx->dir_mode);
>  	if (cifs_sb->ctx->iocharset)
>  		seq_printf(s, ",iocharset=%s", cifs_sb->ctx->iocharset);
> +	if (tcon->ses->unicode == 0)
> +		seq_puts(s, ",nounicode");
> +	else if (tcon->ses->unicode == 1)
> +		seq_puts(s, ",unicode");
>  	if (tcon->seal)
>  		seq_puts(s, ",seal");
>  	else if (tcon->ses->server->ignore_signature)
> diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
> index dcee43889358..2f77b558abe8 100644
> --- a/fs/smb/client/cifsglob.h
> +++ b/fs/smb/client/cifsglob.h
> @@ -651,6 +651,7 @@ struct smb_version_values {
>  	unsigned int	cap_unix;
>  	unsigned int	cap_nt_find;
>  	unsigned int	cap_large_files;
> +	unsigned int	cap_unicode;
>  	__u16		signing_enabled;
>  	__u16		signing_required;
>  	size_t		create_lease_size;
> @@ -1124,6 +1125,7 @@ struct cifs_ses {
>  	bool sign;		/* is signing required? */
>  	bool domainAuto:1;
>  	bool expired_pwd;  /* track if access denied or expired pwd so can know if need to update */
> +	int unicode;
>  	unsigned int flags;
>  	__u16 session_flags;
>  	__u8 smb3signingkey[SMB3_SIGN_KEY_SIZE];
> diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
> index c6f15dbe860a..6218b59b9da7 100644
> --- a/fs/smb/client/cifssmb.c
> +++ b/fs/smb/client/cifssmb.c
> @@ -423,7 +423,10 @@ CIFSSMBNegotiate(const unsigned int xid,
>  		return rc;
>  
>  	pSMB->hdr.Mid = get_next_mid(server);
> -	pSMB->hdr.Flags2 |= (SMBFLG2_UNICODE | SMBFLG2_ERR_STATUS);
> +	pSMB->hdr.Flags2 |= SMBFLG2_ERR_STATUS;
> +
> +	if (ses->unicode != 0)
> +		pSMB->hdr.Flags2 |= SMBFLG2_UNICODE;
>  
>  	if (should_set_ext_sec_flag(ses->sectype)) {
>  		cifs_dbg(FYI, "Requesting extended security\n");
> diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
> index 612816ec71f5..3d9d736b6e58 100644
> --- a/fs/smb/client/connect.c
> +++ b/fs/smb/client/connect.c
> @@ -2338,6 +2338,7 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
>  	ses->cred_uid = ctx->cred_uid;
>  	ses->linux_uid = ctx->linux_uid;
>  
> +	ses->unicode = ctx->unicode;
>  	ses->sectype = ctx->sectype;
>  	ses->sign = ctx->sign;
>  	ses->local_nls = load_nls(ctx->local_nls->charset);
> @@ -3928,7 +3929,7 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
>  		   struct TCP_Server_Info *server,
>  		   struct nls_table *nls_info)
>  {
> -	int rc = -ENOSYS;
> +	int rc = 0;
>  	struct TCP_Server_Info *pserver = SERVER_IS_CHAN(server) ? server->primary_server : server;
>  	struct sockaddr_in6 *addr6 = (struct sockaddr_in6 *)&pserver->dstaddr;
>  	struct sockaddr_in *addr = (struct sockaddr_in *)&pserver->dstaddr;
> @@ -3980,6 +3981,26 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
>  		if (!linuxExtEnabled)
>  			ses->capabilities &= (~server->vals->cap_unix);
>  
> +		/*
> +		 * Check if the server supports specified encoding mode.
> +		 * Zero value in vals->cap_unicode indidcates that chosen
> +		 * protocol dialect does not support non-UNICODE mode.
> +		 */
> +		if (ses->unicode == 1 && server->vals->cap_unicode != 0 &&
> +		    !(server->capabilities & server->vals->cap_unicode)) {
> +			cifs_dbg(VFS, "Server does not support mounting in UNICODE mode\n");
> +			rc = -EOPNOTSUPP;
> +		} else if (ses->unicode == 0 && server->vals->cap_unicode == 0) {
> +			cifs_dbg(VFS, "Server does not support mounting in non-UNICODE mode\n");
> +			rc = -EOPNOTSUPP;
> +		} else if (ses->unicode == 0) {
> +			/*
> +			 * When UNICODE mode was explicitly disabled then
> +			 * do not announce client UNICODE capability.
> +			 */
> +			ses->capabilities &= (~server->vals->cap_unicode);
> +		}
> +
>  		if (ses->auth_key.response) {
>  			cifs_dbg(FYI, "Free previous auth_key.response = %p\n",
>  				 ses->auth_key.response);
> @@ -3992,8 +4013,12 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
>  	cifs_dbg(FYI, "Security Mode: 0x%x Capabilities: 0x%x TimeAdjust: %d\n",
>  		 server->sec_mode, server->capabilities, server->timeAdj);
>  
> -	if (server->ops->sess_setup)
> -		rc = server->ops->sess_setup(xid, ses, server, nls_info);
> +	if (!rc) {
> +		if (server->ops->sess_setup)
> +			rc = server->ops->sess_setup(xid, ses, server, nls_info);
> +		else
> +			rc = -ENOSYS;
> +	}
>  
>  	if (rc) {
>  		cifs_server_dbg(VFS, "Send error in SessSetup = %d\n", rc);
> @@ -4063,6 +4088,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
>  	ctx->seal = master_tcon->seal;
>  	ctx->witness = master_tcon->use_witness;
>  	ctx->dfs_root_ses = master_tcon->ses->dfs_root_ses;
> +	ctx->unicode = master_tcon->ses->unicode;
>  
>  	rc = cifs_set_vol_auth(ctx, master_tcon->ses);
>  	if (rc) {
> diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
> index 7dd46cfc9fb3..d970b66e529c 100644
> --- a/fs/smb/client/fs_context.c
> +++ b/fs/smb/client/fs_context.c
> @@ -127,6 +127,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = {
>  	fsparam_flag("rootfs", Opt_rootfs),
>  	fsparam_flag("compress", Opt_compress),
>  	fsparam_flag("witness", Opt_witness),
> +	fsparam_flag_no("unicode", Opt_unicode),
>  
>  	/* Mount options which take uid or gid */
>  	fsparam_uid("backupuid", Opt_backupuid),
> @@ -930,6 +931,10 @@ static int smb3_verify_reconfigure_ctx(struct fs_context *fc,
>  		cifs_errorf(fc, "can not change iocharset during remount\n");
>  		return -EINVAL;
>  	}
> +	if (new_ctx->unicode != old_ctx->unicode) {
> +		cifs_errorf(fc, "can not change unicode during remount\n");
> +		return -EINVAL;
> +	}
>  
>  	return 0;
>  }
> @@ -1520,6 +1525,10 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
>  		ctx->witness = true;
>  		pr_warn_once("Witness protocol support is experimental\n");
>  		break;
> +	case Opt_unicode:
> +		ctx->unicode = !result.negated;
> +		cifs_dbg(FYI, "unicode set to %d\n", ctx->unicode);
> +		break;
>  	case Opt_rootfs:
>  #ifndef CONFIG_CIFS_ROOT
>  		cifs_dbg(VFS, "rootfs support requires CONFIG_CIFS_ROOT config option\n");
> @@ -1816,6 +1825,8 @@ int smb3_init_fs_context(struct fs_context *fc)
>  	ctx->symlink_type = CIFS_SYMLINK_TYPE_DEFAULT;
>  	ctx->nonativesocket = 0;
>  
> +	ctx->unicode = -1; /* autodetect, but prefer UNICODE mode */
> +
>  /*
>   *	short int override_uid = -1;
>   *	short int override_gid = -1;
> diff --git a/fs/smb/client/fs_context.h b/fs/smb/client/fs_context.h
> index 18d39d457145..1514e05e6629 100644
> --- a/fs/smb/client/fs_context.h
> +++ b/fs/smb/client/fs_context.h
> @@ -127,6 +127,7 @@ enum cifs_param {
>  	Opt_multichannel,
>  	Opt_compress,
>  	Opt_witness,
> +	Opt_unicode,
>  
>  	/* Mount options which take numeric value */
>  	Opt_backupuid,
> @@ -296,6 +297,7 @@ struct smb3_fs_context {
>  	bool compress; /* enable SMB2 messages (READ/WRITE) de/compression */
>  	bool rootfs:1; /* if it's a SMB root file system */
>  	bool witness:1; /* use witness protocol */
> +	int unicode;
>  	char *leaf_fullpath;
>  	struct cifs_ses *dfs_root_ses;
>  	bool dfs_automount:1; /* set for dfs automount only */
> diff --git a/fs/smb/client/sess.c b/fs/smb/client/sess.c
> index c88e9657f47a..6a92db287843 100644
> --- a/fs/smb/client/sess.c
> +++ b/fs/smb/client/sess.c
> @@ -529,6 +529,7 @@ cifs_ses_add_channel(struct cifs_ses *ses,
>  	ctx->password = ses->password;
>  	ctx->sectype = ses->sectype;
>  	ctx->sign = ses->sign;
> +	ctx->unicode = ses->unicode;
>  
>  	/* UNC and paths */
>  	/* XXX: Use ses->server->hostname? */
> diff --git a/fs/smb/client/smb1ops.c b/fs/smb/client/smb1ops.c
> index abca214f923c..b0fb4a5c586d 100644
> --- a/fs/smb/client/smb1ops.c
> +++ b/fs/smb/client/smb1ops.c
> @@ -1189,6 +1189,7 @@ struct smb_version_values smb1_values = {
>  	.cap_unix = CAP_UNIX,
>  	.cap_nt_find = CAP_NT_SMBS | CAP_NT_FIND,
>  	.cap_large_files = CAP_LARGE_FILES,
> +	.cap_unicode = CAP_UNICODE,
>  	.signing_enabled = SECMODE_SIGN_ENABLED,
>  	.signing_required = SECMODE_SIGN_REQUIRED,
>  };
> -- 
> 2.20.1
> 
> 

Hello Björn, I know about iocharset=iso8859-1 mount option, but change
here is something different. As I wrote in the commit message it allows
to easily test that "non-unicode flag of SMB" code path implementation
in cifs.ko that works correctly. For example, thanks to this change I
was able to find few bugs (including parsing of symlinks) in that code
path and fixes for them are in this patch series.

On Friday 15 November 2024 14:26:19 Björn JACKE wrote:
> you can  simply use iocharset=iso8859-1 mount option if you want to get legacy
> charsets on the client side to work. I don't think that it's a good idea to
> mess with the ancient non-unicode flag of SMB.
> 
> Björn
> 
> On 2024-10-28 at 12:03 +0100 Pali Rohár sent off:
> > SMB1 protocol supports non-UNICODE (8-bit OEM character set) and
> > UNICODE (UTF-16) modes.
> > 
> > Linux SMB1 client implements both of them but currently does not allow to
> > choose non-UNICODE mode when SMB1 server announce UNICODE mode support.
> > 
> > This change adds a new mount option -o nounicode to disable UNICODE mode
> > and force usage of non-UNICODE (8-bit OEM character set) mode.
> > 
> > This allows to test non-UNICODE implementation of Linux SMB1 client against
> > any SMB1 server, including modern and recent Windows SMB1 server.
> > 
> > Signed-off-by: Pali Rohár <pali@kernel.org>
> > ---
> >  fs/smb/client/cifsfs.c     |  4 ++++
> >  fs/smb/client/cifsglob.h   |  2 ++
> >  fs/smb/client/cifssmb.c    |  5 ++++-
> >  fs/smb/client/connect.c    | 32 +++++++++++++++++++++++++++++---
> >  fs/smb/client/fs_context.c | 11 +++++++++++
> >  fs/smb/client/fs_context.h |  2 ++
> >  fs/smb/client/sess.c       |  1 +
> >  fs/smb/client/smb1ops.c    |  1 +
> >  8 files changed, 54 insertions(+), 4 deletions(-)
> > 
> > diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
> > index 1decf91d3f61..447ed7831f2c 100644
> > --- a/fs/smb/client/cifsfs.c
> > +++ b/fs/smb/client/cifsfs.c
> > @@ -611,6 +611,10 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
> >  					   cifs_sb->ctx->dir_mode);
> >  	if (cifs_sb->ctx->iocharset)
> >  		seq_printf(s, ",iocharset=%s", cifs_sb->ctx->iocharset);
> > +	if (tcon->ses->unicode == 0)
> > +		seq_puts(s, ",nounicode");
> > +	else if (tcon->ses->unicode == 1)
> > +		seq_puts(s, ",unicode");
> >  	if (tcon->seal)
> >  		seq_puts(s, ",seal");
> >  	else if (tcon->ses->server->ignore_signature)
> > diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
> > index dcee43889358..2f77b558abe8 100644
> > --- a/fs/smb/client/cifsglob.h
> > +++ b/fs/smb/client/cifsglob.h
> > @@ -651,6 +651,7 @@ struct smb_version_values {
> >  	unsigned int	cap_unix;
> >  	unsigned int	cap_nt_find;
> >  	unsigned int	cap_large_files;
> > +	unsigned int	cap_unicode;
> >  	__u16		signing_enabled;
> >  	__u16		signing_required;
> >  	size_t		create_lease_size;
> > @@ -1124,6 +1125,7 @@ struct cifs_ses {
> >  	bool sign;		/* is signing required? */
> >  	bool domainAuto:1;
> >  	bool expired_pwd;  /* track if access denied or expired pwd so can know if need to update */
> > +	int unicode;
> >  	unsigned int flags;
> >  	__u16 session_flags;
> >  	__u8 smb3signingkey[SMB3_SIGN_KEY_SIZE];
> > diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
> > index c6f15dbe860a..6218b59b9da7 100644
> > --- a/fs/smb/client/cifssmb.c
> > +++ b/fs/smb/client/cifssmb.c
> > @@ -423,7 +423,10 @@ CIFSSMBNegotiate(const unsigned int xid,
> >  		return rc;
> >  
> >  	pSMB->hdr.Mid = get_next_mid(server);
> > -	pSMB->hdr.Flags2 |= (SMBFLG2_UNICODE | SMBFLG2_ERR_STATUS);
> > +	pSMB->hdr.Flags2 |= SMBFLG2_ERR_STATUS;
> > +
> > +	if (ses->unicode != 0)
> > +		pSMB->hdr.Flags2 |= SMBFLG2_UNICODE;
> >  
> >  	if (should_set_ext_sec_flag(ses->sectype)) {
> >  		cifs_dbg(FYI, "Requesting extended security\n");
> > diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
> > index 612816ec71f5..3d9d736b6e58 100644
> > --- a/fs/smb/client/connect.c
> > +++ b/fs/smb/client/connect.c
> > @@ -2338,6 +2338,7 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
> >  	ses->cred_uid = ctx->cred_uid;
> >  	ses->linux_uid = ctx->linux_uid;
> >  
> > +	ses->unicode = ctx->unicode;
> >  	ses->sectype = ctx->sectype;
> >  	ses->sign = ctx->sign;
> >  	ses->local_nls = load_nls(ctx->local_nls->charset);
> > @@ -3928,7 +3929,7 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
> >  		   struct TCP_Server_Info *server,
> >  		   struct nls_table *nls_info)
> >  {
> > -	int rc = -ENOSYS;
> > +	int rc = 0;
> >  	struct TCP_Server_Info *pserver = SERVER_IS_CHAN(server) ? server->primary_server : server;
> >  	struct sockaddr_in6 *addr6 = (struct sockaddr_in6 *)&pserver->dstaddr;
> >  	struct sockaddr_in *addr = (struct sockaddr_in *)&pserver->dstaddr;
> > @@ -3980,6 +3981,26 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
> >  		if (!linuxExtEnabled)
> >  			ses->capabilities &= (~server->vals->cap_unix);
> >  
> > +		/*
> > +		 * Check if the server supports specified encoding mode.
> > +		 * Zero value in vals->cap_unicode indidcates that chosen
> > +		 * protocol dialect does not support non-UNICODE mode.
> > +		 */
> > +		if (ses->unicode == 1 && server->vals->cap_unicode != 0 &&
> > +		    !(server->capabilities & server->vals->cap_unicode)) {
> > +			cifs_dbg(VFS, "Server does not support mounting in UNICODE mode\n");
> > +			rc = -EOPNOTSUPP;
> > +		} else if (ses->unicode == 0 && server->vals->cap_unicode == 0) {
> > +			cifs_dbg(VFS, "Server does not support mounting in non-UNICODE mode\n");
> > +			rc = -EOPNOTSUPP;
> > +		} else if (ses->unicode == 0) {
> > +			/*
> > +			 * When UNICODE mode was explicitly disabled then
> > +			 * do not announce client UNICODE capability.
> > +			 */
> > +			ses->capabilities &= (~server->vals->cap_unicode);
> > +		}
> > +
> >  		if (ses->auth_key.response) {
> >  			cifs_dbg(FYI, "Free previous auth_key.response = %p\n",
> >  				 ses->auth_key.response);
> > @@ -3992,8 +4013,12 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
> >  	cifs_dbg(FYI, "Security Mode: 0x%x Capabilities: 0x%x TimeAdjust: %d\n",
> >  		 server->sec_mode, server->capabilities, server->timeAdj);
> >  
> > -	if (server->ops->sess_setup)
> > -		rc = server->ops->sess_setup(xid, ses, server, nls_info);
> > +	if (!rc) {
> > +		if (server->ops->sess_setup)
> > +			rc = server->ops->sess_setup(xid, ses, server, nls_info);
> > +		else
> > +			rc = -ENOSYS;
> > +	}
> >  
> >  	if (rc) {
> >  		cifs_server_dbg(VFS, "Send error in SessSetup = %d\n", rc);
> > @@ -4063,6 +4088,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
> >  	ctx->seal = master_tcon->seal;
> >  	ctx->witness = master_tcon->use_witness;
> >  	ctx->dfs_root_ses = master_tcon->ses->dfs_root_ses;
> > +	ctx->unicode = master_tcon->ses->unicode;
> >  
> >  	rc = cifs_set_vol_auth(ctx, master_tcon->ses);
> >  	if (rc) {
> > diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
> > index 7dd46cfc9fb3..d970b66e529c 100644
> > --- a/fs/smb/client/fs_context.c
> > +++ b/fs/smb/client/fs_context.c
> > @@ -127,6 +127,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = {
> >  	fsparam_flag("rootfs", Opt_rootfs),
> >  	fsparam_flag("compress", Opt_compress),
> >  	fsparam_flag("witness", Opt_witness),
> > +	fsparam_flag_no("unicode", Opt_unicode),
> >  
> >  	/* Mount options which take uid or gid */
> >  	fsparam_uid("backupuid", Opt_backupuid),
> > @@ -930,6 +931,10 @@ static int smb3_verify_reconfigure_ctx(struct fs_context *fc,
> >  		cifs_errorf(fc, "can not change iocharset during remount\n");
> >  		return -EINVAL;
> >  	}
> > +	if (new_ctx->unicode != old_ctx->unicode) {
> > +		cifs_errorf(fc, "can not change unicode during remount\n");
> > +		return -EINVAL;
> > +	}
> >  
> >  	return 0;
> >  }
> > @@ -1520,6 +1525,10 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
> >  		ctx->witness = true;
> >  		pr_warn_once("Witness protocol support is experimental\n");
> >  		break;
> > +	case Opt_unicode:
> > +		ctx->unicode = !result.negated;
> > +		cifs_dbg(FYI, "unicode set to %d\n", ctx->unicode);
> > +		break;
> >  	case Opt_rootfs:
> >  #ifndef CONFIG_CIFS_ROOT
> >  		cifs_dbg(VFS, "rootfs support requires CONFIG_CIFS_ROOT config option\n");
> > @@ -1816,6 +1825,8 @@ int smb3_init_fs_context(struct fs_context *fc)
> >  	ctx->symlink_type = CIFS_SYMLINK_TYPE_DEFAULT;
> >  	ctx->nonativesocket = 0;
> >  
> > +	ctx->unicode = -1; /* autodetect, but prefer UNICODE mode */
> > +
> >  /*
> >   *	short int override_uid = -1;
> >   *	short int override_gid = -1;
> > diff --git a/fs/smb/client/fs_context.h b/fs/smb/client/fs_context.h
> > index 18d39d457145..1514e05e6629 100644
> > --- a/fs/smb/client/fs_context.h
> > +++ b/fs/smb/client/fs_context.h
> > @@ -127,6 +127,7 @@ enum cifs_param {
> >  	Opt_multichannel,
> >  	Opt_compress,
> >  	Opt_witness,
> > +	Opt_unicode,
> >  
> >  	/* Mount options which take numeric value */
> >  	Opt_backupuid,
> > @@ -296,6 +297,7 @@ struct smb3_fs_context {
> >  	bool compress; /* enable SMB2 messages (READ/WRITE) de/compression */
> >  	bool rootfs:1; /* if it's a SMB root file system */
> >  	bool witness:1; /* use witness protocol */
> > +	int unicode;
> >  	char *leaf_fullpath;
> >  	struct cifs_ses *dfs_root_ses;
> >  	bool dfs_automount:1; /* set for dfs automount only */
> > diff --git a/fs/smb/client/sess.c b/fs/smb/client/sess.c
> > index c88e9657f47a..6a92db287843 100644
> > --- a/fs/smb/client/sess.c
> > +++ b/fs/smb/client/sess.c
> > @@ -529,6 +529,7 @@ cifs_ses_add_channel(struct cifs_ses *ses,
> >  	ctx->password = ses->password;
> >  	ctx->sectype = ses->sectype;
> >  	ctx->sign = ses->sign;
> > +	ctx->unicode = ses->unicode;
> >  
> >  	/* UNC and paths */
> >  	/* XXX: Use ses->server->hostname? */
> > diff --git a/fs/smb/client/smb1ops.c b/fs/smb/client/smb1ops.c
> > index abca214f923c..b0fb4a5c586d 100644
> > --- a/fs/smb/client/smb1ops.c
> > +++ b/fs/smb/client/smb1ops.c
> > @@ -1189,6 +1189,7 @@ struct smb_version_values smb1_values = {
> >  	.cap_unix = CAP_UNIX,
> >  	.cap_nt_find = CAP_NT_SMBS | CAP_NT_FIND,
> >  	.cap_large_files = CAP_LARGE_FILES,
> > +	.cap_unicode = CAP_UNICODE,
> >  	.signing_enabled = SECMODE_SIGN_ENABLED,
> >  	.signing_required = SECMODE_SIGN_REQUIRED,
> >  };
> > -- 
> > 2.20.1
> > 
> >