Re: [PATCH 1/4] cifs: Add support for creating SFU symlinks

From: Steve French
Date: Sun Sep 15 2024 - 17:15:31 EST

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merged into cifs-2.6.git for-next pending review/testing

On Sun, Sep 15, 2024 at 2:46 PM Pali Rohár <pali@xxxxxxxxxx> wrote:
>
> Linux cifs client can already detect SFU symlinks and reads it content
> (target location). But currently is not able to create new symlink. So
> implement this missing support.
>
> When 'sfu' mount option is specified and 'mfsymlinks' is not specified then
> create new symlinks in SFU-style. This will provide full SFU compatibility
> of symlinks when mounting cifs share with 'sfu' option. 'mfsymlinks' option
> override SFU for better Apple compatibility as explained in fs_context.c
> file in smb3_update_mnt_flags() function.
>
> Extend __cifs_sfu_make_node() function, which now can handle also S_IFLNK
> type and refactor structures passed to sync_write() in this function, by
> splitting SFU type and SFU data from original combined struct win_dev as
> combined fixed-length struct cannot be used for variable-length symlinks.
>
> Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
> ---
> fs/smb/client/cifspdu.h | 6 ---
> fs/smb/client/cifsproto.h | 4 ++
> fs/smb/client/fs_context.c | 13 ++++---
> fs/smb/client/link.c | 3 ++
> fs/smb/client/smb2ops.c | 80 +++++++++++++++++++++++++++++---------
> 5 files changed, 77 insertions(+), 29 deletions(-)
>
> diff --git a/fs/smb/client/cifspdu.h b/fs/smb/client/cifspdu.h
> index a2072ab9e586..c3b6263060b0 100644
> --- a/fs/smb/client/cifspdu.h
> +++ b/fs/smb/client/cifspdu.h
> @@ -2573,12 +2573,6 @@ typedef struct {
> } __attribute__((packed)) FIND_FILE_STANDARD_INFO; /* level 0x1 FF resp data */
>
>
> -struct win_dev {
> - unsigned char type[8]; /* IntxCHR or IntxBLK or LnxFIFO or LnxSOCK */
> - __le64 major;
> - __le64 minor;
> -} __attribute__((packed));
> -
> struct fea {
> unsigned char EA_flags;
> __u8 name_len;
> diff --git a/fs/smb/client/cifsproto.h b/fs/smb/client/cifsproto.h
> index 497bf3c447bc..791bddac0396 100644
> --- a/fs/smb/client/cifsproto.h
> +++ b/fs/smb/client/cifsproto.h
> @@ -676,6 +676,10 @@ char *extract_sharename(const char *unc);
> int parse_reparse_point(struct reparse_data_buffer *buf,
> u32 plen, struct cifs_sb_info *cifs_sb,
> 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,
> + const char *full_path, umode_t mode, dev_t dev,
> + const char *symname);
> int cifs_sfu_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);
> diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
> index bc926ab2555b..2f0c3894b0f7 100644
> --- a/fs/smb/client/fs_context.c
> +++ b/fs/smb/client/fs_context.c
> @@ -1896,14 +1896,17 @@ void smb3_update_mnt_flags(struct cifs_sb_info *cifs_sb)
> if (ctx->mfsymlinks) {
> if (ctx->sfu_emul) {
> /*
> - * Our SFU ("Services for Unix" emulation does not allow
> - * creating symlinks but does allow reading existing SFU
> - * symlinks (it does allow both creating and reading SFU
> - * style mknod and FIFOs though). When "mfsymlinks" and
> + * Our SFU ("Services for Unix") emulation allows now
> + * creating new and reading existing SFU symlinks.
> + * Older Linux kernel versions were not able to neither
> + * read existing nor create new SFU symlinks. But
> + * creating and reading SFU style mknod and FIFOs was
> + * supported for long time. When "mfsymlinks" and
> * "sfu" are both enabled at the same time, it allows
> * reading both types of symlinks, but will only create
> * them with mfsymlinks format. This allows better
> - * Apple compatibility (probably better for Samba too)
> + * Apple compatibility, compatibility with older Linux
> + * kernel clients (probably better for Samba too)
> * while still recognizing old Windows style symlinks.
> */
> cifs_dbg(VFS, "mount options mfsymlinks and sfu both enabled\n");
> diff --git a/fs/smb/client/link.c b/fs/smb/client/link.c
> index 80099bbb333b..47ddeb7fa111 100644
> --- a/fs/smb/client/link.c
> +++ b/fs/smb/client/link.c
> @@ -606,6 +606,9 @@ cifs_symlink(struct mnt_idmap *idmap, struct inode *inode,
> /* BB what if DFS and this volume is on different share? BB */
> if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) {
> rc = create_mf_symlink(xid, pTcon, cifs_sb, full_path, symname);
> + } else if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL) {
> + rc = __cifs_sfu_make_node(xid, inode, direntry, pTcon,
> + full_path, S_IFLNK, 0, symname);
> #ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
> } else if (pTcon->unix_ext) {
> rc = CIFSUnixCreateSymLink(xid, pTcon, full_path, symname,
> diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
> index 9c2d065d3cc4..2c251e9a3a30 100644
> --- a/fs/smb/client/smb2ops.c
> +++ b/fs/smb/client/smb2ops.c
> @@ -5055,9 +5055,10 @@ static int smb2_next_header(struct TCP_Server_Info *server, char *buf,
> return 0;
> }
>
> -static int __cifs_sfu_make_node(unsigned int xid, struct inode *inode,
> +int __cifs_sfu_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)
> + const char *full_path, umode_t mode, dev_t dev,
> + const char *symname)
> {
> struct TCP_Server_Info *server = tcon->ses->server;
> struct cifs_open_parms oparms;
> @@ -5065,30 +5066,64 @@ static int __cifs_sfu_make_node(unsigned int xid, struct inode *inode,
> struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
> struct cifs_fid fid;
> unsigned int bytes_written;
> - struct win_dev pdev = {};
> - struct kvec iov[2];
> + u8 type[8];
> + int type_len = 0;
> + struct {
> + __le64 major;
> + __le64 minor;
> + } __packed pdev = {};
> + __le16 *symname_utf16 = NULL;
> + u8 *data = NULL;
> + int data_len = 0;
> + struct kvec iov[3];
> __u32 oplock = server->oplocks ? REQ_OPLOCK : 0;
> int rc;
>
> switch (mode & S_IFMT) {
> case S_IFCHR:
> - memcpy(pdev.type, "IntxCHR\0", 8);
> + type_len = 8;
> + memcpy(type, "IntxCHR\0", type_len);
> pdev.major = cpu_to_le64(MAJOR(dev));
> pdev.minor = cpu_to_le64(MINOR(dev));
> + data = (u8 *)&pdev;
> + data_len = sizeof(pdev);
> break;
> case S_IFBLK:
> - memcpy(pdev.type, "IntxBLK\0", 8);
> + type_len = 8;
> + memcpy(type, "IntxBLK\0", type_len);
> pdev.major = cpu_to_le64(MAJOR(dev));
> pdev.minor = cpu_to_le64(MINOR(dev));
> + data = (u8 *)&pdev;
> + data_len = sizeof(pdev);
> + break;
> + case S_IFLNK:
> + type_len = 8;
> + memcpy(type, "IntxLNK\1", type_len);
> + symname_utf16 = cifs_strndup_to_utf16(symname, strlen(symname),
> + &data_len, cifs_sb->local_nls,
> + NO_MAP_UNI_RSVD);
> + if (!symname_utf16) {
> + rc = -ENOMEM;
> + goto out;
> + }
> + data_len -= 2; /* symlink is without trailing wide-nul */
> + data = (u8 *)symname_utf16;
> break;
> case S_IFSOCK:
> - strscpy(pdev.type, "LnxSOCK");
> + type_len = 8;
> + strscpy(type, "LnxSOCK");
> + data = (u8 *)&pdev;
> + data_len = sizeof(pdev);
> break;
> case S_IFIFO:
> - strscpy(pdev.type, "LnxFIFO");
> + type_len = 8;
> + strscpy(type, "LnxFIFO");
> + data = (u8 *)&pdev;
> + data_len = sizeof(pdev);
> break;
> default:
> - return -EPERM;
> + rc = -EPERM;
> + goto out;
> }
>
> oparms = CIFS_OPARMS(cifs_sb, tcon, full_path, GENERIC_WRITE,
> @@ -5098,17 +5133,26 @@ static int __cifs_sfu_make_node(unsigned int xid, struct inode *inode,
>
> rc = server->ops->open(xid, &oparms, &oplock, NULL);
> if (rc)
> - return rc;
> + goto out;
>
> - io_parms.pid = current->tgid;
> - io_parms.tcon = tcon;
> - io_parms.length = sizeof(pdev);
> - iov[1].iov_base = &pdev;
> - iov[1].iov_len = sizeof(pdev);
> + if (type_len + data_len > 0) {
> + io_parms.pid = current->tgid;
> + io_parms.tcon = tcon;
> + io_parms.length = type_len + data_len;
> + iov[1].iov_base = type;
> + iov[1].iov_len = type_len;
> + iov[2].iov_base = data;
> + iov[2].iov_len = data_len;
> +
> + rc = server->ops->sync_write(xid, &fid, &io_parms,
> + &bytes_written,
> + iov, ARRAY_SIZE(iov)-1);
> + }
>
> - rc = server->ops->sync_write(xid, &fid, &io_parms,
> - &bytes_written, iov, 1);
> server->ops->close(xid, tcon, &fid);
> +
> +out:
> + kfree(symname_utf16);
> return rc;
> }
>
> @@ -5120,7 +5164,7 @@ int cifs_sfu_make_node(unsigned int xid, struct inode *inode,
> int rc;
>
> rc = __cifs_sfu_make_node(xid, inode, dentry, tcon,
> - full_path, mode, dev);
> + full_path, mode, dev, NULL);
> if (rc)
> return rc;
>
> --
> 2.20.1
>
>

--
Thanks,

Steve

Next message: Pablo Neira Ayuso: "Re: [PATCH net v1 1/1] netfilter: nf_reject: Fix build error when CONFIG_BRIDGE_NETFILTER=n"
Previous message: Steve French: "Re: [PATCH 4/4] cifs: Update SFU comments about fifos and sockets"
In reply to: Pali Rohár: "[PATCH 1/4] cifs: Add support for creating SFU symlinks"
Next in thread: Pali Rohár: "[PATCH 3/4] cifs: Fix creating of SFU fifo special files"
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