cifs: Fix parsing native symlinks relative to the export

[ Upstream commit 723f4ef90452aa629f3d923e92e0449d69362b1d ]

SMB symlink which has SYMLINK_FLAG_RELATIVE set is relative (as opposite of
the absolute) and it can be relative either to the current directory (where
is the symlink stored) or relative to the top level export path. To what it
is relative depends on the first character of the symlink target path.

If the first character is path separator then symlink is relative to the
export, otherwise to the current directory. Linux (and generally POSIX
systems) supports only symlink paths relative to the current directory
where is symlink stored.

Currently if Linux SMB client reads relative SMB symlink with first
character as path separator (slash), it let as is. Which means that Linux
interpret it as absolute symlink pointing from the root (/). But this
location is different than the top level directory of SMB export (unless
SMB export was mounted to the root) and thefore SMB symlinks relative to
the export are interpreted wrongly by Linux SMB client.

Fix this problem. As Linux does not have equivalent of the path relative to
the top of the mount point, convert such symlink target path relative to
the current directory. Do this by prepending "../" pattern N times before
the SMB target path, where N is the number of path separators found in SMB
symlink path.

So for example, if SMB share is mounted to Linux path /mnt/share/, symlink
is stored in file /mnt/share/test/folder1/symlink (so SMB symlink path is
test\folder1\symlink) and SMB symlink target points to \test\folder2\file,
then convert symlink target path to Linux path ../../test/folder2/file.

Deduplicate code for parsing SMB symlinks in native form from functions
smb2_parse_symlink_response() and parse_reparse_native_symlink() into new
function smb2_parse_native_symlink() and pass into this new function a new
full_path parameter from callers, which specify SMB full path where is
symlink stored.

This change fixes resolving of the native Windows symlinks relative to the
top level directory of the SMB share.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Stable-dep-of: f4ca4f5a36ea ("cifs: Fix parsing reparse point with native symlink in SMB1 non-UNICODE session")
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 1dfedb64ffcbcd2ca21eb61a351df21e8841c8e5..64610236cc7251c58d43f7a88ec97d811ca8edff 100644 (file)
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -589,6 +589,7 @@ struct smb_version_operations {
        /* Check for STATUS_NETWORK_NAME_DELETED */
        bool (*is_network_name_deleted)(char *buf, struct TCP_Server_Info *srv);
        int (*parse_reparse_point)(struct cifs_sb_info *cifs_sb,
+                                  const char *full_path,
                                   struct kvec *rsp_iov,
                                   struct cifs_open_info_data *data);
        int (*create_reparse_symlink)(const unsigned int xid,

diff --git a/fs/smb/client/cifsproto.h b/fs/smb/client/cifsproto.h
index 497bf3c447bcb59486feed877560bd920d91a70e..8d35a5cab39e350ccab25aa2059d0755e958b5e7 100644 (file)
--- a/fs/smb/client/cifsproto.h
+++ b/fs/smb/client/cifsproto.h
@@ -675,6 +675,7 @@ char *extract_hostname(const char *unc);
 char *extract_sharename(const char *unc);
 int parse_reparse_point(struct reparse_data_buffer *buf,
                        u32 plen, struct cifs_sb_info *cifs_sb,
+                       const char *full_path,
                        bool unicode, struct cifs_open_info_data *data);
 int cifs_sfu_make_node(unsigned int xid, struct inode *inode,
                       struct dentry *dentry, struct cifs_tcon *tcon,

diff --git a/fs/smb/client/inode.c b/fs/smb/client/inode.c
index ede36884be8ae20f4632f42fb0db9ac4c3e67e39..200936773a9560fe33d2b4240d8b0952410351c5 100644 (file)
--- a/fs/smb/client/inode.c
+++ b/fs/smb/client/inode.c
@@ -1075,6 +1075,7 @@ static int reparse_info_to_fattr(struct cifs_open_info_data *data,
                        rc = 0;
                } else if (iov && server->ops->parse_reparse_point) {
                        rc = server->ops->parse_reparse_point(cifs_sb,
+                                                             full_path,
                                                              iov, data);
                }
                break;

diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 90da1e2b6217b6afe00f4cff9be601e8a5aff2d7..f74d0a86f44a4e81f5884f3a4acbc5c71f19d985 100644 (file)
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -535,9 +535,76 @@ static int parse_reparse_posix(struct reparse_posix_data *buf,
        return 0;
 }
 
+int smb2_parse_native_symlink(char **target, const char *buf, unsigned int len,
+                             bool unicode, bool relative,
+                             const char *full_path,
+                             struct cifs_sb_info *cifs_sb)
+{
+       char sep = CIFS_DIR_SEP(cifs_sb);
+       char *linux_target = NULL;
+       char *smb_target = NULL;
+       int levels;
+       int rc;
+       int i;
+
+       smb_target = cifs_strndup_from_utf16(buf, len, unicode, cifs_sb->local_nls);
+       if (!smb_target) {
+               rc = -ENOMEM;
+               goto out;
+       }
+
+       if (smb_target[0] == sep && relative) {
+               /*
+                * This is a relative SMB symlink from the top of the share,
+                * which is the top level directory of the Linux mount point.
+                * Linux does not support such relative symlinks, so convert
+                * it to the relative symlink from the current directory.
+                * full_path is the SMB path to the symlink (from which is
+                * extracted current directory) and smb_target is the SMB path
+                * where symlink points, therefore full_path must always be on
+                * the SMB share.
+                */
+               int smb_target_len = strlen(smb_target)+1;
+               levels = 0;
+               for (i = 1; full_path[i]; i++) { /* i=1 to skip leading sep */
+                       if (full_path[i] == sep)
+                               levels++;
+               }
+               linux_target = kmalloc(levels*3 + smb_target_len, GFP_KERNEL);
+               if (!linux_target) {
+                       rc = -ENOMEM;
+                       goto out;
+               }
+               for (i = 0; i < levels; i++) {
+                       linux_target[i*3 + 0] = '.';
+                       linux_target[i*3 + 1] = '.';
+                       linux_target[i*3 + 2] = sep;
+               }
+               memcpy(linux_target + levels*3, smb_target+1, smb_target_len); /* +1 to skip leading sep */
+       } else {
+               linux_target = smb_target;
+               smb_target = NULL;
+       }
+
+       if (sep == '\\')
+               convert_delimiter(linux_target, '/');
+
+       rc = 0;
+       *target = linux_target;
+
+       cifs_dbg(FYI, "%s: symlink target: %s\n", __func__, *target);
+
+out:
+       if (rc != 0)
+               kfree(linux_target);
+       kfree(smb_target);
+       return rc;
+}
+
 static int parse_reparse_symlink(struct reparse_symlink_data_buffer *sym,
                                 u32 plen, bool unicode,
                                 struct cifs_sb_info *cifs_sb,
+                                const char *full_path,
                                 struct cifs_open_info_data *data)
 {
        unsigned int len;
@@ -552,20 +619,18 @@ static int parse_reparse_symlink(struct reparse_symlink_data_buffer *sym,
                return -EIO;
        }
 
-       data->symlink_target = cifs_strndup_from_utf16(sym->PathBuffer + offs,
-                                                      len, unicode,
-                                                      cifs_sb->local_nls);
-       if (!data->symlink_target)
-               return -ENOMEM;
-
-       convert_delimiter(data->symlink_target, '/');
-       cifs_dbg(FYI, "%s: target path: %s\n", __func__, data->symlink_target);
-
-       return 0;
+       return smb2_parse_native_symlink(&data->symlink_target,
+                                        sym->PathBuffer + offs,
+                                        len,
+                                        unicode,
+                                        le32_to_cpu(sym->Flags) & SYMLINK_FLAG_RELATIVE,
+                                        full_path,
+                                        cifs_sb);
 }
 
 int parse_reparse_point(struct reparse_data_buffer *buf,
                        u32 plen, struct cifs_sb_info *cifs_sb,
+                       const char *full_path,
                        bool unicode, struct cifs_open_info_data *data)
 {
        struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
@@ -580,7 +645,7 @@ int parse_reparse_point(struct reparse_data_buffer *buf,
        case IO_REPARSE_TAG_SYMLINK:
                return parse_reparse_symlink(
                        (struct reparse_symlink_data_buffer *)buf,
-                       plen, unicode, cifs_sb, data);
+                       plen, unicode, cifs_sb, full_path, data);
        case IO_REPARSE_TAG_LX_SYMLINK:
        case IO_REPARSE_TAG_AF_UNIX:
        case IO_REPARSE_TAG_LX_FIFO:
@@ -596,6 +661,7 @@ int parse_reparse_point(struct reparse_data_buffer *buf,
 }
 
 int smb2_parse_reparse_point(struct cifs_sb_info *cifs_sb,
+                            const char *full_path,
                             struct kvec *rsp_iov,
                             struct cifs_open_info_data *data)
 {
@@ -605,7 +671,7 @@ int smb2_parse_reparse_point(struct cifs_sb_info *cifs_sb,
 
        buf = (struct reparse_data_buffer *)((u8 *)io +
                                             le32_to_cpu(io->OutputOffset));
-       return parse_reparse_point(buf, plen, cifs_sb, true, data);
+       return parse_reparse_point(buf, plen, cifs_sb, full_path, true, data);
 }
 
 static void wsl_to_fattr(struct cifs_open_info_data *data,

diff --git a/fs/smb/client/reparse.h b/fs/smb/client/reparse.h
index 2a9f4f9f79de08c40cf66f63b2a5c511bd59c4ad..ff05b0e75c92840668b3798843c8d624b4dcd498 100644 (file)
--- a/fs/smb/client/reparse.h
+++ b/fs/smb/client/reparse.h
@@ -117,7 +117,9 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode,
 int smb2_mknod_reparse(unsigned int xid, struct inode *inode,
                       struct dentry *dentry, struct cifs_tcon *tcon,
                       const char *full_path, umode_t mode, dev_t dev);
-int smb2_parse_reparse_point(struct cifs_sb_info *cifs_sb, struct kvec *rsp_iov,
+int smb2_parse_reparse_point(struct cifs_sb_info *cifs_sb,
+                            const char *full_path,
+                            struct kvec *rsp_iov,
                             struct cifs_open_info_data *data);
 
 #endif /* _CIFS_REPARSE_H */

diff --git a/fs/smb/client/smb1ops.c b/fs/smb/client/smb1ops.c
index 8c03250d85ae0c4d5bc1738143fb88989e213381..3c7f3c4b94c8dce318abb911d81ce107a3a9c457 100644 (file)
--- a/fs/smb/client/smb1ops.c
+++ b/fs/smb/client/smb1ops.c
@@ -994,6 +994,7 @@ static int cifs_query_symlink(const unsigned int xid,
 }
 
 static int cifs_parse_reparse_point(struct cifs_sb_info *cifs_sb,
+                                   const char *full_path,
                                    struct kvec *rsp_iov,
                                    struct cifs_open_info_data *data)
 {
@@ -1004,7 +1005,7 @@ static int cifs_parse_reparse_point(struct cifs_sb_info *cifs_sb,
 
        buf = (struct reparse_data_buffer *)((__u8 *)&io->hdr.Protocol +
                                             le32_to_cpu(io->DataOffset));
-       return parse_reparse_point(buf, plen, cifs_sb, unicode, data);
+       return parse_reparse_point(buf, plen, cifs_sb, full_path, unicode, data);
 }
 
 static bool

diff --git a/fs/smb/client/smb2file.c b/fs/smb/client/smb2file.c
index c23478ab1cf851999e6578eed9d9f6b99cc08b30..dc52995f5591054103a2f4a13a099c799934b567 100644 (file)
--- a/fs/smb/client/smb2file.c
+++ b/fs/smb/client/smb2file.c
@@ -63,12 +63,12 @@ static struct smb2_symlink_err_rsp *symlink_data(const struct kvec *iov)
        return sym;
 }
 
-int smb2_parse_symlink_response(struct cifs_sb_info *cifs_sb, const struct kvec *iov, char **path)
+int smb2_parse_symlink_response(struct cifs_sb_info *cifs_sb, const struct kvec *iov,
+                               const char *full_path, char **path)
 {
        struct smb2_symlink_err_rsp *sym;
        unsigned int sub_offs, sub_len;
        unsigned int print_offs, print_len;
-       char *s;
 
        if (!cifs_sb || !iov || !iov->iov_base || !iov->iov_len || !path)
                return -EINVAL;
@@ -86,15 +86,13 @@ int smb2_parse_symlink_response(struct cifs_sb_info *cifs_sb, const struct kvec
            iov->iov_len < SMB2_SYMLINK_STRUCT_SIZE + print_offs + print_len)
                return -EINVAL;
 
-       s = cifs_strndup_from_utf16((char *)sym->PathBuffer + sub_offs, sub_len, true,
-                                   cifs_sb->local_nls);
-       if (!s)
-               return -ENOMEM;
-       convert_delimiter(s, '/');
-       cifs_dbg(FYI, "%s: symlink target: %s\n", __func__, s);
-
-       *path = s;
-       return 0;
+       return smb2_parse_native_symlink(path,
+                                        (char *)sym->PathBuffer + sub_offs,
+                                        sub_len,
+                                        true,
+                                        le32_to_cpu(sym->Flags) & SYMLINK_FLAG_RELATIVE,
+                                        full_path,
+                                        cifs_sb);
 }
 
 int smb2_open_file(const unsigned int xid, struct cifs_open_parms *oparms, __u32 *oplock, void *buf)
@@ -126,6 +124,7 @@ int smb2_open_file(const unsigned int xid, struct cifs_open_parms *oparms, __u32
                        goto out;
                if (hdr->Status == STATUS_STOPPED_ON_SYMLINK) {
                        rc = smb2_parse_symlink_response(oparms->cifs_sb, &err_iov,
+                                                        oparms->path,
                                                         &data->symlink_target);
                        if (!rc) {
                                memset(smb2_data, 0, sizeof(*smb2_data));

diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
index cdb0e028e73c4614b64094d298138593c8ba0183..9a28a30ec1a3440f59785459c48cbebabe6456d8 100644 (file)
--- a/fs/smb/client/smb2inode.c
+++ b/fs/smb/client/smb2inode.c
@@ -828,6 +828,7 @@ finished:
 
 static int parse_create_response(struct cifs_open_info_data *data,
                                 struct cifs_sb_info *cifs_sb,
+                                const char *full_path,
                                 const struct kvec *iov)
 {
        struct smb2_create_rsp *rsp = iov->iov_base;
@@ -841,6 +842,7 @@ static int parse_create_response(struct cifs_open_info_data *data,
                break;
        case STATUS_STOPPED_ON_SYMLINK:
                rc = smb2_parse_symlink_response(cifs_sb, iov,
+                                                full_path,
                                                 &data->symlink_target);
                if (rc)
                        return rc;
@@ -930,14 +932,14 @@ int smb2_query_path_info(const unsigned int xid,
 
        switch (rc) {
        case 0:
-               rc = parse_create_response(data, cifs_sb, &out_iov[0]);
+               rc = parse_create_response(data, cifs_sb, full_path, &out_iov[0]);
                break;
        case -EOPNOTSUPP:
                /*
                 * BB TODO: When support for special files added to Samba
                 * re-verify this path.
                 */
-               rc = parse_create_response(data, cifs_sb, &out_iov[0]);
+               rc = parse_create_response(data, cifs_sb, full_path, &out_iov[0]);
                if (rc || !data->reparse_point)
                        goto out;
 

diff --git a/fs/smb/client/smb2proto.h b/fs/smb/client/smb2proto.h
index 5e0855fefcfe66eb3af8c8f455f04c74bfbc8ffb..aa01ae234732a15897625de94dff684bfb5d95eb 100644 (file)
--- a/fs/smb/client/smb2proto.h
+++ b/fs/smb/client/smb2proto.h
@@ -113,7 +113,14 @@ extern int smb3_query_mf_symlink(unsigned int xid, struct cifs_tcon *tcon,
                          struct cifs_sb_info *cifs_sb,
                          const unsigned char *path, char *pbuf,
                          unsigned int *pbytes_read);
-int smb2_parse_symlink_response(struct cifs_sb_info *cifs_sb, const struct kvec *iov, char **path);
+int smb2_parse_native_symlink(char **target, const char *buf, unsigned int len,
+                             bool unicode, bool relative,
+                             const char *full_path,
+                             struct cifs_sb_info *cifs_sb);
+int smb2_parse_symlink_response(struct cifs_sb_info *cifs_sb,
+                               const struct kvec *iov,
+                               const char *full_path,
+                               char **path);
 int smb2_open_file(const unsigned int xid, struct cifs_open_parms *oparms, __u32 *oplock,
                   void *buf);
 extern int smb2_unlock_range(struct cifsFileInfo *cfile,