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-rw-r--r--fs/smb/client/fs_context.c22
-rw-r--r--fs/smb/client/fs_context.h2
-rw-r--r--fs/smb/client/reparse.c267
3 files changed, 273 insertions, 18 deletions
diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index 5381f05420bc..d7d2f6c607b5 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -185,6 +185,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = {
fsparam_string("cache", Opt_cache),
fsparam_string("reparse", Opt_reparse),
fsparam_string("upcall_target", Opt_upcalltarget),
+ fsparam_string("symlinkroot", Opt_symlinkroot),
/* Arguments that should be ignored */
fsparam_flag("guest", Opt_ignore),
@@ -386,6 +387,7 @@ smb3_fs_context_dup(struct smb3_fs_context *new_ctx, struct smb3_fs_context *ctx
new_ctx->iocharset = NULL;
new_ctx->leaf_fullpath = NULL;
new_ctx->dns_dom = NULL;
+ new_ctx->symlinkroot = NULL;
/*
* Make sure to stay in sync with smb3_cleanup_fs_context_contents()
*/
@@ -401,6 +403,7 @@ smb3_fs_context_dup(struct smb3_fs_context *new_ctx, struct smb3_fs_context *ctx
DUP_CTX_STR(iocharset);
DUP_CTX_STR(leaf_fullpath);
DUP_CTX_STR(dns_dom);
+ DUP_CTX_STR(symlinkroot);
return 0;
}
@@ -1727,6 +1730,16 @@ 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 ... */
@@ -1735,6 +1748,13 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
goto cifs_parse_mount_err;
}
+ /*
+ * 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:
@@ -1867,6 +1887,8 @@ smb3_cleanup_fs_context_contents(struct smb3_fs_context *ctx)
ctx->leaf_fullpath = NULL;
kfree(ctx->dns_dom);
ctx->dns_dom = 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 8813533345ee..43bc3119af21 100644
--- a/fs/smb/client/fs_context.h
+++ b/fs/smb/client/fs_context.h
@@ -166,6 +166,7 @@ enum cifs_param {
Opt_cache,
Opt_reparse,
Opt_upcalltarget,
+ Opt_symlinkroot,
/* Mount options to be ignored */
Opt_ignore,
@@ -296,6 +297,7 @@ struct smb3_fs_context {
enum cifs_reparse_type reparse_type;
bool dfs_conn:1; /* set for dfs mounts */
char *dns_dom;
+ 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 3be2173a026d..344371dd895c 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -25,36 +25,131 @@ 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;
if (strlen(symname) > REPARSE_SYM_PATH_MAX)
return -ENAMETOOLONG;
- 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] = cpu_to_le16('\\');
+ path[1] = path[2] = cpu_to_le16('?');
+ path[5] = cpu_to_le16(':');
+ }
+
/*
* SMB distinguish between symlink to directory and symlink to file.
* They cannot be exchanged (symlink of file type which points to
@@ -67,8 +162,18 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode,
if (rc < 0)
goto out;
- plen = 2 * UniStrnlen((wchar_t *)path, REPARSE_SYM_PATH_MAX);
- len = sizeof(*buf) + plen * 2;
+ slen = 2 * UniStrnlen((wchar_t *)path, REPARSE_SYM_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;
@@ -77,17 +182,17 @@ 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,
@@ -98,6 +203,7 @@ 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);
@@ -543,6 +649,9 @@ 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;
@@ -570,7 +679,123 @@ 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.
@@ -599,6 +824,12 @@ 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;
}
generated by cgit v1.2.3 (git 2.39.0) at 2025-07-25 01:05:26 +0300