I have figured it out. There is a new member at the end of the struct smb3_fs_context. I have resolved this rebase conflict and pushed update of this change into my cifs branch (based on 6.12-rc2) at: https://git.kernel.org/pub/scm/linux/kernel/git/pali/linux.git/log/?h=cifs Beware that this branch contains also some other WIP patches which I have not sent yet. If needed I can resend just this one rebased patch to the list. On Sunday 06 October 2024 22:59:18 Steve French wrote: > This patch had a merge conflict in fs_context.h and wouldn't apply > cleanly. Do you have a git branch with this series (or all three > recent patch series) applied on 6.12-rc2? > > On Sat, Oct 5, 2024 at 9:04 AM Pali Rohár <pali@xxxxxxxxxx> wrote: > > > > If the SMB symlink is stored on NT server in absolute form then it points > > to the NT object hierarchy, which is different from POSIX one and needs > > some conversion / mapping. > > > > To make interoperability with Windows SMB server and WSL subsystem, reuse > > its logic of mapping between NT paths and POSIX paths into Linux SMB > > client. > > > > WSL subsystem on Windows uses for -t drvfs mount option -o symlinkroot= > > which specifies the POSIX path where are expected to be mounted lowercase > > Windows drive letters (without colon). > > > > Do same for Linux SMB client and add a new mount option -o symlinkroot= > > which mimics the drvfs mount option of the same name. It specifies where in > > the Linux VFS hierarchy is the root of the DOS / Windows drive letters, and > > translates between absolute NT-style symlinks and absolute Linux VFS > > symlinks. Default value of symlinkroot is "/mnt", same what is using WSL. > > > > Note that DOS / Windows drive letter symlinks are just subset of all > > possible NT-style symlinks. Drive letters live in NT subtree \??\ and > > important details about NT paths and object hierarchy are in the comments > > in this change. > > > > When symlink target location from non-POSIX SMB server is in absolute form > > (indicated by absence of SYMLINK_FLAG_RELATIVE) then it is converted to > > Linux absolute symlink according to symlinkroot configuration. > > > > And when creating a new symlink on non-POSIX SMB server in absolute form > > then Linux absolute target is converted to NT-style according to > > symlinkroot configuration. > > > > When SMB server is POSIX, then this change does not affect neither reading > > target location of symlink, nor creating a new symlink. It is expected that > > POSIX SMB server works with POSIX paths where the absolute root is /. > > > > This change improves interoperability of absolute SMB symlinks with Windows > > SMB servers. > > > > Signed-off-by: Pali Rohár <pali@xxxxxxxxxx> > > --- > > fs/smb/client/fs_context.c | 22 +++ > > fs/smb/client/fs_context.h | 2 + > > fs/smb/client/reparse.c | 267 ++++++++++++++++++++++++++++++++++--- > > 3 files changed, 273 insertions(+), 18 deletions(-) > > > > diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c > > index 2f0c3894b0f7..22b550860cc8 100644 > > --- a/fs/smb/client/fs_context.c > > +++ b/fs/smb/client/fs_context.c > > @@ -178,6 +178,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = { > > fsparam_string("sec", Opt_sec), > > fsparam_string("cache", Opt_cache), > > fsparam_string("reparse", Opt_reparse), > > + fsparam_string("symlinkroot", Opt_symlinkroot), > > > > /* Arguments that should be ignored */ > > fsparam_flag("guest", Opt_ignore), > > @@ -355,6 +356,7 @@ smb3_fs_context_dup(struct smb3_fs_context *new_ctx, struct smb3_fs_context *ctx > > new_ctx->source = NULL; > > new_ctx->iocharset = NULL; > > new_ctx->leaf_fullpath = NULL; > > + new_ctx->symlinkroot = NULL; > > /* > > * Make sure to stay in sync with smb3_cleanup_fs_context_contents() > > */ > > @@ -369,6 +371,7 @@ smb3_fs_context_dup(struct smb3_fs_context *new_ctx, struct smb3_fs_context *ctx > > DUP_CTX_STR(nodename); > > DUP_CTX_STR(iocharset); > > DUP_CTX_STR(leaf_fullpath); > > + DUP_CTX_STR(symlinkroot); > > > > return 0; > > } > > @@ -1614,9 +1617,26 @@ static int smb3_fs_context_parse_param(struct fs_context *fc, > > if (parse_reparse_flavor(fc, param->string, ctx)) > > goto cifs_parse_mount_err; > > break; > > + case Opt_symlinkroot: > > + if (param->string[0] != '/') { > > + cifs_errorf(fc, "symlinkroot mount options must be absolute path\n"); > > + goto cifs_parse_mount_err; > > + } > > + kfree(ctx->symlinkroot); > > + ctx->symlinkroot = kstrdup(param->string, GFP_KERNEL); > > + if (!ctx->symlinkroot) > > + goto cifs_parse_mount_err; > > + break; > > } > > /* case Opt_ignore: - is ignored as expected ... */ > > > > + /* > > + * By default resolve all native absolute symlinks relative to "/mnt/". > > + * Same default has drvfs driver running in WSL for resolving SMB shares. > > + */ > > + if (!ctx->symlinkroot) > > + ctx->symlinkroot = kstrdup("/mnt/", GFP_KERNEL); > > + > > return 0; > > > > cifs_parse_mount_err: > > @@ -1747,6 +1767,8 @@ smb3_cleanup_fs_context_contents(struct smb3_fs_context *ctx) > > ctx->prepath = NULL; > > kfree(ctx->leaf_fullpath); > > ctx->leaf_fullpath = NULL; > > + kfree(ctx->symlinkroot); > > + ctx->symlinkroot = NULL; > > } > > > > void > > diff --git a/fs/smb/client/fs_context.h b/fs/smb/client/fs_context.h > > index cf577ec0dd0a..8dd12498ffd8 100644 > > --- a/fs/smb/client/fs_context.h > > +++ b/fs/smb/client/fs_context.h > > @@ -157,6 +157,7 @@ enum cifs_param { > > Opt_sec, > > Opt_cache, > > Opt_reparse, > > + Opt_symlinkroot, > > > > /* Mount options to be ignored */ > > Opt_ignore, > > @@ -284,6 +285,7 @@ struct smb3_fs_context { > > struct cifs_ses *dfs_root_ses; > > bool dfs_automount:1; /* set for dfs automount only */ > > enum cifs_reparse_type reparse_type; > > + char *symlinkroot; /* top level directory for native SMB symlinks in absolute format */ > > }; > > > > extern const struct fs_parameter_spec smb3_fs_parameters[]; > > diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c > > index fb1d16b17f38..a577b2d2a4fc 100644 > > --- a/fs/smb/client/reparse.c > > +++ b/fs/smb/client/reparse.c > > @@ -25,33 +25,128 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode, > > const char *full_path, const char *symname) > > { > > struct reparse_symlink_data_buffer *buf = NULL; > > - struct cifs_open_info_data data; > > + 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; > > + __le16 *path = NULL; > > bool directory; > > - char *sym, sep = CIFS_DIR_SEP(cifs_sb); > > - u16 len, plen; > > + char *symlink_target = NULL; > > + char *sym = NULL; > > + char sep = CIFS_DIR_SEP(cifs_sb); > > + u16 len, plen, poff, slen; > > int rc = 0; > > > > - sym = kstrdup(symname, GFP_KERNEL); > > - if (!sym) > > - return -ENOMEM; > > + symlink_target = kstrdup(symname, GFP_KERNEL); > > + if (!symlink_target) { > > + rc = -ENOMEM; > > + goto out; > > + } > > > > data = (struct cifs_open_info_data) { > > .reparse_point = true, > > .reparse = { .tag = IO_REPARSE_TAG_SYMLINK, }, > > - .symlink_target = sym, > > + .symlink_target = symlink_target, > > }; > > > > - convert_delimiter(sym, sep); > > + if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) && symname[0] == '/') { > > + /* > > + * This is a request to create an absolute symlink on the server > > + * which does not support POSIX paths, and expects symlink in > > + * NT-style path. So convert absolute Linux symlink target path > > + * to the absolute NT-style path. Root of the NT-style path for > > + * symlinks is specified in "symlinkroot" mount option. This will > > + * ensure compatibility of this symlink stored in absolute form > > + * on the SMB server. > > + */ > > + if (!strstarts(symname, cifs_sb->ctx->symlinkroot)) { > > + /* > > + * If the absolute Linux symlink target path is not > > + * inside "symlinkroot" location then there is no way > > + * to convert such Linux symlink to NT-style path. > > + */ > > + cifs_dbg(VFS, > > + "absolute symlink '%s' cannot be converted to NT format " > > + "because it is outside of symlinkroot='%s'\n", > > + symname, cifs_sb->ctx->symlinkroot); > > + rc = -EINVAL; > > + goto out; > > + } > > + len = strlen(cifs_sb->ctx->symlinkroot); > > + if (cifs_sb->ctx->symlinkroot[len-1] != '/') > > + len++; > > + if (symname[len] >= 'a' && symname[len] <= 'z' && > > + (symname[len+1] == '/' || symname[len+1] == '\0')) { > > + /* > > + * Symlink points to Linux target /symlinkroot/x/path/... > > + * where 'x' is the lowercase local Windows drive. > > + * NT-style path for 'x' has common form \??\X:\path\... > > + * with uppercase local Windows drive. > > + */ > > + int common_path_len = strlen(symname+len+1)+1; > > + sym = kzalloc(6+common_path_len, GFP_KERNEL); > > + if (!sym) { > > + rc = -ENOMEM; > > + goto out; > > + } > > + memcpy(sym, "\\??\\", 4); > > + sym[4] = symname[len] - ('a'-'A'); > > + sym[5] = ':'; > > + memcpy(sym+6, symname+len+1, common_path_len); > > + } else { > > + /* Unhandled absolute symlink. Report an error. */ > > + cifs_dbg( > > + VFS, > > + "absolute symlink '%s' cannot be converted to NT format " > > + "because it points to unknown target\n", > > + symname); > > + rc = -EINVAL; > > + goto out; > > + } > > + } else { > > + /* > > + * This is request to either create an absolute symlink on > > + * server which expects POSIX paths or it is an request to > > + * create a relative symlink from the current directory. > > + * These paths have same format as relative SMB symlinks, > > + * so no conversion is needed. So just take symname as-is. > > + */ > > + sym = kstrdup(symname, GFP_KERNEL); > > + if (!sym) { > > + rc = -ENOMEM; > > + goto out; > > + } > > + } > > + > > + if (sep == '\\') > > + convert_delimiter(sym, sep); > > + > > + /* > > + * For absolute NT symlinks it is required to pass also leading > > + * backslash and to not mangle NT object prefix "\\??\\" and not to > > + * mangle colon in drive letter. But cifs_convert_path_to_utf16() > > + * removes leading backslash and replaces '?' and ':'. So temporary > > + * mask these characters in NT object prefix by '_' and then change > > + * them back. > > + */ > > + if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) && symname[0] == '/') > > + sym[0] = sym[1] = sym[2] = sym[5] = '_'; > > + > > path = cifs_convert_path_to_utf16(sym, cifs_sb); > > if (!path) { > > rc = -ENOMEM; > > goto out; > > } > > > > + if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) && symname[0] == '/') { > > + sym[0] = '\\'; > > + sym[1] = sym[2] = '?'; > > + sym[5] = ':'; > > + path[0] = '\\'; > > + path[1] = path[2] = '?'; > > + path[5] = ':'; > > + } > > + > > /* > > * SMB distinguish between symlink to directory and symlink to file. > > * They cannot be exchanged (symlink of file type which points to > > @@ -64,8 +159,18 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode, > > if (rc < 0) > > goto out; > > > > - plen = 2 * UniStrnlen((wchar_t *)path, PATH_MAX); > > - len = sizeof(*buf) + plen * 2; > > + slen = 2 * UniStrnlen((wchar_t *)path, PATH_MAX); > > + poff = 0; > > + plen = slen; > > + if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) && symname[0] == '/') { > > + /* > > + * For absolute NT symlinks skip leading "\\??\\" in PrintName as > > + * PrintName is user visible location in DOS/Win32 format (not in NT format). > > + */ > > + poff = 4; > > + plen -= 2 * poff; > > + } > > + len = sizeof(*buf) + plen + slen; > > buf = kzalloc(len, GFP_KERNEL); > > if (!buf) { > > rc = -ENOMEM; > > @@ -74,17 +179,17 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode, > > > > 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->SubstituteNameLength = cpu_to_le16(slen); > > + memcpy(&buf->PathBuffer[plen], path, slen); > > + > > buf->PrintNameOffset = 0; > > buf->PrintNameLength = cpu_to_le16(plen); > > - memcpy(buf->PathBuffer, path, plen); > > + memcpy(buf->PathBuffer, path+poff, plen); > > + > > buf->Flags = cpu_to_le32(*symname != '/' ? SYMLINK_FLAG_RELATIVE : 0); > > - if (*sym != sep) > > - buf->Flags = cpu_to_le32(SYMLINK_FLAG_RELATIVE); > > > > - convert_delimiter(sym, '/'); > > iov.iov_base = buf; > > iov.iov_len = len; > > new = smb2_get_reparse_inode(&data, inode->i_sb, xid, > > @@ -95,6 +200,7 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode, > > else > > rc = PTR_ERR(new); > > out: > > + kfree(sym); > > kfree(path); > > cifs_free_open_info(&data); > > kfree(buf); > > @@ -540,6 +646,9 @@ int smb2_parse_native_symlink(char **target, const char *buf, unsigned int len, > > char sep = CIFS_DIR_SEP(cifs_sb); > > char *linux_target = NULL; > > char *smb_target = NULL; > > + int symlinkroot_len; > > + int abs_path_len; > > + char *abs_path; > > int levels; > > int rc; > > int i; > > @@ -569,7 +678,123 @@ int smb2_parse_native_symlink(char **target, const char *buf, unsigned int len, > > goto out; > > } > > > > - if (smb_target[0] == sep && relative) { > > + if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) && !relative) { > > + /* > > + * This is an absolute symlink from the server which does not > > + * support POSIX paths, so the symlink is in NT-style path. > > + * So convert it to absolute Linux symlink target path. Root of > > + * the NT-style path for symlinks is specified in "symlinkroot" > > + * mount option. > > + * > > + * Root of the DOS and Win32 paths is at NT path \??\ > > + * It means that DOS/Win32 path C:\folder\file.txt is > > + * NT path \??\C:\folder\file.txt > > + * > > + * NT systems have some well-known object symlinks in their NT > > + * hierarchy, which is needed to take into account when resolving > > + * other symlinks. Most commonly used symlink paths are: > > + * \?? -> \GLOBAL?? > > + * \DosDevices -> \?? > > + * \GLOBAL??\GLOBALROOT -> \ > > + * \GLOBAL??\Global -> \GLOBAL?? > > + * \GLOBAL??\NUL -> \Device\Null > > + * \GLOBAL??\UNC -> \Device\Mup > > + * \GLOBAL??\PhysicalDrive0 -> \Device\Harddisk0\DR0 (for each harddisk) > > + * \GLOBAL??\A: -> \Device\Floppy0 (if A: is the first floppy) > > + * \GLOBAL??\C: -> \Device\HarddiskVolume1 (if C: is the first harddisk) > > + * \GLOBAL??\D: -> \Device\CdRom0 (if D: is first cdrom) > > + * \SystemRoot -> \Device\Harddisk0\Partition1\WINDOWS (or where is NT system installed) > > + * \Volume{...} -> \Device\HarddiskVolume1 (where ... is system generated guid) > > + * > > + * In most common cases, absolute NT symlinks points to path on > > + * DOS/Win32 drive letter, system-specific Volume or on UNC share. > > + * Here are few examples of commonly used absolute NT symlinks > > + * created by mklink.exe tool: > > + * \??\C:\folder\file.txt > > + * \??\\C:\folder\file.txt > > + * \??\UNC\server\share\file.txt > > + * \??\\UNC\server\share\file.txt > > + * \??\Volume{b75e2c83-0000-0000-0000-602f00000000}\folder\file.txt > > + * > > + * It means that the most common path prefix \??\ is also NT path > > + * symlink (to \GLOBAL??). It is less common that second path > > + * separator is double backslash, but it is valid. > > + * > > + * Volume guid is randomly generated by the target system and so > > + * only the target system knows the mapping between guid and the > > + * hardisk number. Over SMB it is not possible to resolve this > > + * mapping, therefore symlinks pointing to target location of > > + * volume guids are totally unusable over SMB. > > + * > > + * For now parse only symlink paths available for DOS and Win32. > > + * Those are paths with \??\ prefix or paths which points to \??\ > > + * via other NT symlink (\DosDevices\, \GLOBAL??\, ...). > > + */ > > + abs_path = smb_target; > > +globalroot: > > + if (strstarts(abs_path, "\\??\\")) > > + abs_path += sizeof("\\??\\")-1; > > + else if (strstarts(abs_path, "\\DosDevices\\")) > > + abs_path += sizeof("\\DosDevices\\")-1; > > + else if (strstarts(abs_path, "\\GLOBAL??\\")) > > + abs_path += sizeof("\\GLOBAL??\\")-1; > > + else { > > + /* Unhandled absolute symlink, points outside of DOS/Win32 */ > > + cifs_dbg(VFS, > > + "absolute symlink '%s' cannot be converted from NT format " > > + "because points to unknown target\n", > > + smb_target); > > + rc = -EIO; > > + goto out; > > + } > > + > > + /* Sometimes path separator after \?? is double backslash */ > > + if (abs_path[0] == '\\') > > + abs_path++; > > + > > + while (strstarts(abs_path, "Global\\")) > > + abs_path += sizeof("Global\\")-1; > > + > > + if (strstarts(abs_path, "GLOBALROOT\\")) { > > + /* Label globalroot requires path with leading '\\', so do not trim '\\' */ > > + abs_path += sizeof("GLOBALROOT")-1; > > + goto globalroot; > > + } > > + > > + /* For now parse only paths to drive letters */ > > + if (((abs_path[0] >= 'A' && abs_path[0] <= 'Z') || > > + (abs_path[0] >= 'a' && abs_path[0] <= 'z')) && > > + abs_path[1] == ':' && > > + (abs_path[2] == '\\' || abs_path[2] == '\0')) { > > + /* Convert drive letter to lowercase and drop colon */ > > + char drive_letter = abs_path[0]; > > + if (drive_letter >= 'A' && drive_letter <= 'Z') > > + drive_letter += 'a'-'A'; > > + abs_path++; > > + abs_path[0] = drive_letter; > > + } else { > > + /* Unhandled absolute symlink. Report an error. */ > > + cifs_dbg(VFS, > > + "absolute symlink '%s' cannot be converted from NT format " > > + "because points to unknown target\n", > > + smb_target); > > + rc = -EIO; > > + goto out; > > + } > > + > > + abs_path_len = strlen(abs_path)+1; > > + symlinkroot_len = strlen(cifs_sb->ctx->symlinkroot); > > + if (cifs_sb->ctx->symlinkroot[symlinkroot_len-1] == '/') > > + symlinkroot_len--; > > + linux_target = kmalloc(symlinkroot_len + 1 + abs_path_len, GFP_KERNEL); > > + if (!linux_target) { > > + rc = -ENOMEM; > > + goto out; > > + } > > + memcpy(linux_target, cifs_sb->ctx->symlinkroot, symlinkroot_len); > > + linux_target[symlinkroot_len] = '/'; > > + memcpy(linux_target + symlinkroot_len + 1, abs_path, abs_path_len); > > + } else 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. > > @@ -598,6 +823,12 @@ int smb2_parse_native_symlink(char **target, const char *buf, unsigned int len, > > } > > memcpy(linux_target + levels*3, smb_target+1, smb_target_len); /* +1 to skip leading sep */ > > } else { > > + /* > > + * This is either an absolute symlink in POSIX-style format > > + * or relative SMB symlink from the current directory. > > + * These paths have same format as Linux symlinks, so no > > + * conversion is needed. > > + */ > > linux_target = smb_target; > > smb_target = NULL; > > } > > -- > > 2.20.1 > > > > > > > -- > Thanks, > > Steve
