[PATCH 6.6 016/102] smb: client: allow creating symlinks via reparse points

Greg Kroah-Hartman
2024-05-23T13:23:22Z

From: Paulo Alcantara <pc@manguebit.com>

[ Upstream commit 514d793e27a310eb26b112c1f8f1a160472907e5 ]

Add support for creating symlinks via IO_REPARSE_TAG_SYMLINK reparse
points in SMB2+.

These are fully supported by most SMB servers and documented in
MS-FSCC. Also have the advantage of requiring fewer roundtrips as
their symlink targets can be parsed directly from CREATE responses on
STATUS_STOPPED_ON_SYMLINK errors.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202311260838.nx5mkj1j-lkp@intel.com/
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/smb/client/cifsglob.h | 6 ++++
fs/smb/client/link.c | 15 ++++++---
fs/smb/client/smb2ops.c | 70 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 86 insertions(+), 5 deletions(-)

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 3e7c3c3d73a73..414648bf816b2 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -577,6 +577,12 @@ struct smb_version_operations {
int (*parse_reparse_point)(struct cifs_sb_info *cifs_sb,
struct kvec *rsp_iov,
struct cifs_open_info_data *data);
+ int (*create_reparse_symlink)(const unsigned int xid,
+ struct inode *inode,
+ struct dentry *dentry,
+ struct cifs_tcon *tcon,
+ const char *full_path,
+ const char *symname);
};

struct smb_version_values {
diff --git a/fs/smb/client/link.c b/fs/smb/client/link.c
index 691f43a1ec2bc..d86da949a9190 100644
--- a/fs/smb/client/link.c
+++ b/fs/smb/client/link.c
@@ -569,6 +569,7 @@ cifs_symlink(struct mnt_idmap *idmap, struct inode *inode,
int rc = -EOPNOTSUPP;
unsigned int xid;
struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
+ struct TCP_Server_Info *server;
struct tcon_link *tlink;
struct cifs_tcon *pTcon;
const char *full_path;
@@ -590,6 +591,7 @@ cifs_symlink(struct mnt_idmap *idmap, struct inode *inode,
goto symlink_exit;
}
pTcon = tlink_tcon(tlink);
+ server = cifs_pick_channel(pTcon->ses);

full_path = build_path_from_dentry(direntry, page);
if (IS_ERR(full_path)) {
@@ -601,17 +603,20 @@ cifs_symlink(struct mnt_idmap *idmap, struct inode *inode,
cifs_dbg(FYI, "symname is %s\n", symname);

/* BB what if DFS and this volume is on different share? BB */
- if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
+ if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) {
rc = create_mf_symlink(xid, pTcon, cifs_sb, full_path, symname);
#ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
- else if (pTcon->unix_ext)
+ } else if (pTcon->unix_ext) {
rc = CIFSUnixCreateSymLink(xid, pTcon, full_path, symname,
cifs_sb->local_nls,
cifs_remap(cifs_sb));
#endif /* CONFIG_CIFS_ALLOW_INSECURE_LEGACY */
- /* else
- rc = CIFSCreateReparseSymLink(xid, pTcon, fromName, toName,
- cifs_sb_target->local_nls); */
+ } else if (server->ops->create_reparse_symlink) {
+ rc = server->ops->create_reparse_symlink(xid, inode, direntry,
+ pTcon, full_path,
+ symname);
+ goto symlink_exit;
+ }

if (rc == 0) {
if (pTcon->posix_extensions) {
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 4fed19d5a81d4..c5957deb1a859 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -5246,6 +5246,72 @@ static int nfs_make_node(unsigned int xid, struct inode *inode,
return rc;
}

+static 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)
+{
+ struct reparse_symlink_data_buffer *buf = NULL;
+ struct cifs_open_info_data data;
+ struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
+ struct inode *new;
+ struct kvec iov;
+ __le16 *path;
+ char *sym;
+ u16 len, plen;
+ int rc = 0;
+
+ sym = kstrdup(symname, GFP_KERNEL);
+ if (!sym)
+ return -ENOMEM;
+
+ data = (struct cifs_open_info_data) {
+ .reparse_point = true,
+ .reparse = { .tag = IO_REPARSE_TAG_SYMLINK, },
+ .symlink_target = sym,
+ };
+
+ path = cifs_convert_path_to_utf16(symname, cifs_sb);
+ if (!path) {
+ rc = -ENOMEM;
+ goto out;
+ }
+
+ plen = 2 * UniStrnlen((wchar_t *)path, PATH_MAX);
+ len = sizeof(*buf) + plen * 2;
+ buf = kzalloc(len, GFP_KERNEL);
+ if (!buf) {
+ rc = -ENOMEM;
+ goto out;
+ }
+
+ buf->ReparseTag = cpu_to_le32(IO_REPARSE_TAG_SYMLINK);
+ buf->ReparseDataLength = cpu_to_le16(len - sizeof(struct reparse_data_buffer));
+ buf->SubstituteNameOffset = cpu_to_le16(plen);
+ buf->SubstituteNameLength = cpu_to_le16(plen);
+ memcpy(&buf->PathBuffer[plen], path, plen);
+ buf->PrintNameOffset = 0;
+ buf->PrintNameLength = cpu_to_le16(plen);
+ memcpy(buf->PathBuffer, path, plen);
+ buf->Flags = cpu_to_le32(*symname != '/' ? SYMLINK_FLAG_RELATIVE : 0);
+
+ iov.iov_base = buf;
+ iov.iov_len = len;
+ new = smb2_get_reparse_inode(&data, inode->i_sb, xid,
+ tcon, full_path, &iov);
+ if (!IS_ERR(new))
+ d_instantiate(dentry, new);
+ else
+ rc = PTR_ERR(new);
+out:
+ kfree(path);
+ cifs_free_open_info(&data);
+ kfree(buf);
+ return rc;
+}
+
static int smb2_make_node(unsigned int xid, struct inode *inode,
struct dentry *dentry, struct cifs_tcon *tcon,
const char *full_path, umode_t mode, dev_t dev)
@@ -5322,6 +5388,7 @@ struct smb_version_operations smb20_operations = {
.parse_reparse_point = smb2_parse_reparse_point,
.query_mf_symlink = smb3_query_mf_symlink,
.create_mf_symlink = smb3_create_mf_symlink,
+ .create_reparse_symlink = smb2_create_reparse_symlink,
.open = smb2_open_file,
.set_fid = smb2_set_fid,
.close = smb2_close_file,
@@ -5424,6 +5491,7 @@ struct smb_version_operations smb21_operations = {
.parse_reparse_point = smb2_parse_reparse_point,
.query_mf_symlink = smb3_query_mf_symlink,
.create_mf_symlink = smb3_create_mf_symlink,
+ .create_reparse_symlink = smb2_create_reparse_symlink,
.open = smb2_open_file,
.set_fid = smb2_set_fid,
.close = smb2_close_file,
@@ -5530,6 +5598,7 @@ struct smb_version_operations smb30_operations = {
.parse_reparse_point = smb2_parse_reparse_point,
.query_mf_symlink = smb3_query_mf_symlink,
.create_mf_symlink = smb3_create_mf_symlink,
+ .create_reparse_symlink = smb2_create_reparse_symlink,
.open = smb2_open_file,
.set_fid = smb2_set_fid,
.close = smb2_close_file,
@@ -5645,6 +5714,7 @@ struct smb_version_operations smb311_operations = {
.parse_reparse_point = smb2_parse_reparse_point,
.query_mf_symlink = smb3_query_mf_symlink,
.create_mf_symlink = smb3_create_mf_symlink,
+ .create_reparse_symlink = smb2_create_reparse_symlink,
.open = smb2_open_file,
.set_fid = smb2_set_fid,
.close = smb2_close_file,
--
2.43.0