On Sunday 06 October 2024 12:00:45 Pali Rohár wrote:
> This change implements support for creating new symlink in WSL-style by
> Linux cifs client when -o reparse=wsl mount option is specified. WSL-style
> symlink uses reparse point with tag IO_REPARSE_TAG_LX_SYMLINK and symlink
> target location is stored in reparse buffer in UTF-8 encoding prefixed by
> 32-bit flags. Flags bits are unknown, but it was observed that WSL always
> sets flags to value 0x02000000. Do same in Linux cifs client.
>
> New symlinks would be created in WSL-style only in case the mount option
> -o reparse=wsl is specified, which is not by default. So default CIFS
> mounts are not affected by this change.
>
> Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
> ---
> fs/smb/client/reparse.c | 65 +++++++++++++++++++++++++++++++++--------
> 1 file changed, 53 insertions(+), 12 deletions(-)
>
> diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
> index 402eb568f466..6606c40487ae 100644
> --- a/fs/smb/client/reparse.c
> +++ b/fs/smb/client/reparse.c
> @@ -506,9 +506,17 @@ static int mknod_nfs(unsigned int xid, struct inode *inode,
> return rc;
> }
>
> -static int wsl_set_reparse_buf(struct reparse_data_buffer *buf,
> - mode_t mode, struct kvec *iov)
> +static int wsl_set_reparse_buf(struct reparse_data_buffer **buf,
> + mode_t mode, const char *symname,
> + struct cifs_sb_info *cifs_sb,
> + struct kvec *iov)
> {
> + struct reparse_wsl_symlink_data_buffer *symlink_buf;
> + __le16 *symname_utf16;
> + int symname_utf16_len;
> + int symname_utf8_maxlen;
> + int symname_utf8_len;
> + size_t buf_len;
> u32 tag;
>
> switch ((tag = reparse_mode_wsl_tag(mode))) {
> @@ -516,17 +524,45 @@ static int wsl_set_reparse_buf(struct reparse_data_buffer *buf,
> case IO_REPARSE_TAG_LX_CHR:
> case IO_REPARSE_TAG_LX_FIFO:
> case IO_REPARSE_TAG_AF_UNIX:
> + buf_len = sizeof(struct reparse_data_buffer);
> + *buf = kzalloc(buf_len, GFP_KERNEL);
> + if (!*buf)
> + return -ENOMEM;
> + break;
> + case IO_REPARSE_TAG_LX_SYMLINK:
> + symname_utf16 = cifs_strndup_to_utf16(symname, strlen(symname),
> + &symname_utf16_len,
> + cifs_sb->local_nls,
> + NO_MAP_UNI_RSVD);
> + if (!symname_utf16)
> + return -ENOMEM;
> + symname_utf8_maxlen = symname_utf16_len/2*3;
> + symlink_buf = kzalloc(sizeof(struct reparse_wsl_symlink_data_buffer) +
> + symname_utf8_maxlen, GFP_KERNEL);
> + if (!symlink_buf) {
> + kfree(symname_utf16);
> + return -ENOMEM;
> + }
> + /* Flag 0x02000000 is unknown, but all wsl symlinks have this value */
> + symlink_buf->Flags = cpu_to_le32(0x02000000);
> + /* PathBuffer is in UTF-8 but without trailing null-term byte */
> + symname_utf8_len = utf16s_to_utf8s(symname_utf16, symname_utf16_len/2,
> + UTF16_LITTLE_ENDIAN,
> + symlink_buf->PathBuffer,
> + symname_utf8_maxlen);
> + *buf = (struct reparse_data_buffer *)symlink_buf;
> + buf_len = sizeof(struct reparse_wsl_symlink_data_buffer) + symname_utf8_len;
> + kfree(symname_utf16);
> break;
> - case IO_REPARSE_TAG_LX_SYMLINK: /* TODO: add support for WSL symlinks */
> default:
> return -EOPNOTSUPP;
> }
>
> - buf->ReparseTag = cpu_to_le32(tag);
> - buf->Reserved = 0;
> - buf->ReparseDataLength = 0;
> - iov->iov_base = buf;
> - iov->iov_len = sizeof(*buf);
> + (*buf)->ReparseTag = cpu_to_le32(tag);
> + (*buf)->Reserved = 0;
> + (*buf)->ReparseDataLength = buf_len - sizeof(struct reparse_data_buffer);
ReparseDataLength is in little endian, so it should be:
(*buf)->ReparseDataLength = cpu_to_le16(buf_len - sizeof(struct reparse_data_buffer));
> + iov->iov_base = *buf;
> + iov->iov_len = buf_len;
> return 0;
> }
>
> @@ -618,25 +654,29 @@ static int mknod_wsl(unsigned int xid, struct inode *inode,
> const char *full_path, umode_t mode, dev_t dev,
> const char *symname)
> {
> + struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
> struct cifs_open_info_data data;
> - struct reparse_data_buffer buf;
> + struct reparse_data_buffer *buf;
> struct smb2_create_ea_ctx *cc;
> struct inode *new;
> unsigned int len;
> struct kvec reparse_iov, xattr_iov;
> int rc;
>
> - rc = wsl_set_reparse_buf(&buf, mode, &reparse_iov);
> + rc = wsl_set_reparse_buf(&buf, mode, symname, cifs_sb, &reparse_iov);
> if (rc)
> return rc;
>
> rc = wsl_set_xattrs(inode, mode, dev, &xattr_iov);
> - if (rc)
> + if (rc) {
> + kfree(buf);
> return rc;
> + }
>
> data = (struct cifs_open_info_data) {
> .reparse_point = true,
> - .reparse = { .tag = le32_to_cpu(buf.ReparseTag), .buf = &buf, },
> + .reparse = { .tag = le32_to_cpu(buf->ReparseTag), .buf = buf, },
> + .symlink_target = kstrdup(symname, GFP_KERNEL),
> };
>
> cc = xattr_iov.iov_base;
> @@ -653,6 +693,7 @@ static int mknod_wsl(unsigned int xid, struct inode *inode,
> rc = PTR_ERR(new);
> cifs_free_open_info(&data);
> kfree(xattr_iov.iov_base);
> + kfree(buf);
> return rc;
> }
>
> --
> 2.20.1
>
