From 2eb74eef4b7eda8df593d22fb48e94ef959ec8a5 Mon Sep 17 00:00:00 2001 From: Carl Johnson Date: Tue, 21 Jul 2026 13:27:55 -0400 Subject: [PATCH] smb: client: handle STATUS_STOPPED_ON_SYMLINK responses without a symlink target MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The macOS built-in SMB server returns STATUS_STOPPED_ON_SYMLINK for a CREATE on a path whose final component is a symlink, but it does not include a Symbolic Link Error Response in the error data: both ErrorContextCount and ByteCount are zero, so the symlink target is not present in the response at all. Per [MS-SMB2] section 2.2.2 such a response should carry a valid Symbolic Link Error Response, so this is a server bug, but the target can still be retrieved with FSCTL_GET_REPARSE_POINT. Frame from a capture against macOS 26.5.2 (build 25F84): SMB2 hdr : Status=0x8000002d STATUS_STOPPED_ON_SYMLINK, Cmd=Create Error Rsp: StructureSize=0x0009 Error Context Count: 0 Byte Count: 0 Error Data: 00 symlink_data() cannot find a struct smb2_symlink_err_rsp in such a response and returns -EINVAL, which parse_create_response() propagates, so smb2_query_path_info() bails out at if (rc || !data->reparse_point) goto out; before it can retry with SMB2_OP_GET_REPARSE. stat(), readlink() and ls of any server-side symlink then fail with -EINVAL: $ ls -la Config l????????? ? ? ? ? ? Config.json $ stat Config/Config.json stat: cannot statx 'Config/Config.json': Invalid argument A 5.10 client resolves these symlinks correctly against the same server and share, so this is a regression for Apple SMB servers. Handle it in several places: - symlink_data() detects the empty response (ErrorContextCount and ByteCount both zero) and returns a distinct -ENODATA, so that "server did not send the target" can be told apart from a genuinely malformed response and only this case is worked around. - parse_create_response() treats -ENODATA like STATUS_IO_REPARSE_TAG_NOT_HANDLED, which does not carry the target either: leave the reparse tag unset and clear rc, so the existing SMB2_OP_GET_REPARSE path retrieves the target. - smb2_query_path_info() only fixes up the symlink target type when the target is already known. SMB2_OP_GET_REPARSE sets data->reparse.tag but does not parse the target out of the reparse buffer; that happens later, in reparse_info_to_fattr(). Without this check smb2_fix_symlink_target_type() is called with a NULL target and returns -EIO. This could not happen with servers that send the target inline and therefore skip SMB2_OP_GET_REPARSE. - smb2_open_file() maps -ENODATA to -EIO, matching STATUS_IO_REPARSE_TAG_NOT_HANDLED, so its callers retrieve the target with SMB2_OP_GET_REPARSE as well. Tested on Debian 13, kernel 6.18.38 (armv7), against macOS 26.5.2: symlinks now resolve, including relative, parent-traversing and directory symlinks, and reads through symlinks succeed. Cc: stable@vger.kernel.org Co-developed-by: Pali Rohár Signed-off-by: Pali Rohár Signed-off-by: Carl Johnson Signed-off-by: Steve French --- fs/smb/client/smb2file.c | 21 +++++++++++++++++++++ fs/smb/client/smb2inode.c | 23 ++++++++++++++++++++--- 2 files changed, 41 insertions(+), 3 deletions(-) diff --git a/fs/smb/client/smb2file.c b/fs/smb/client/smb2file.c index 5ef919bce52d0..f35b6488d810d 100644 --- a/fs/smb/client/smb2file.c +++ b/fs/smb/client/smb2file.c @@ -30,6 +30,19 @@ static struct smb2_symlink_err_rsp *symlink_data(const struct kvec *iov) u8 *end = (u8 *)err + iov->iov_len; u32 len; + /* + * Per [MS-SMB2] section 2.2.2, a STATUS_STOPPED_ON_SYMLINK response has to + * carry a Symbolic Link Error Response, so ByteCount cannot be zero. Some + * servers (e.g. the macOS built-in SMB server) violate this and return an + * empty error response, with both ErrorContextCount and ByteCount set to + * zero, i.e. without the symlink target. Detect this and return -ENODATA + * so that callers can tell "server did not send the target" apart from a + * malformed response, and retrieve the target with FSCTL_GET_REPARSE_POINT + * instead. + */ + if (!err->ErrorContextCount && !le32_to_cpu(err->ByteCount)) + return ERR_PTR(-ENODATA); + if (err->ErrorContextCount) { struct smb2_error_context_rsp *p; @@ -199,6 +212,14 @@ int smb2_open_file(const unsigned int xid, struct cifs_open_parms *oparms, rc = smb2_parse_symlink_response(oparms->cifs_sb, &err_iov, oparms->path, &data->symlink_target); + /* + * If smb2_parse_symlink_response returned -ENODATA then the + * symlink_target was not sent. Treat this as if the SMB2_open() + * failed with STATUS_IO_REPARSE_TAG_NOT_HANDLED status, which is + * indicated by the -EIO errno. + */ + if (rc == -ENODATA) + rc = -EIO; if (!rc) { memset(&data->fi, 0, sizeof(data->fi)); oparms->create_options |= OPEN_REPARSE_POINT; diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c index 6c9c229b91f65..213bc298cdf22 100644 --- a/fs/smb/client/smb2inode.c +++ b/fs/smb/client/smb2inode.c @@ -792,9 +792,19 @@ static int parse_create_response(struct cifs_open_info_data *data, rc = smb2_parse_symlink_response(cifs_sb, iov, full_path, &data->symlink_target); - if (rc) + if (rc != 0 && rc != -ENODATA) return rc; - tag = IO_REPARSE_TAG_SYMLINK; + /* + * -ENODATA means that the response was parsed but did not contain + * the symlink target at all (see symlink_data()). Treat it like + * STATUS_IO_REPARSE_TAG_NOT_HANDLED, which does not contain it + * either: leave the tag unset and clear rc, so that the caller + * retrieves the target with SMB2_OP_GET_REPARSE. + */ + if (rc == -ENODATA) + rc = 0; + else + tag = IO_REPARSE_TAG_SYMLINK; reparse_point = true; break; case STATUS_SUCCESS: @@ -987,7 +997,14 @@ int smb2_query_path_info(const unsigned int xid, rc = -EOPNOTSUPP; } - if (data->reparse.tag == IO_REPARSE_TAG_SYMLINK && !rc) { + /* + * If the symlink was already parsed in create response then it is needed to fix + * its type now (after the second call with OPEN_REPARSE_POINT which filled the + * data->fi.Attributes). If the symlink was not parsed in create response then + * the data->symlink_target was not filled yet and then the type will be fixed + * later after data->symlink_target is filled. + */ + if (data->reparse.tag == IO_REPARSE_TAG_SYMLINK && !rc && data->symlink_target) { bool directory = le32_to_cpu(data->fi.Attributes) & ATTR_DIRECTORY; rc = smb2_fix_symlink_target_type(&data->symlink_target, directory, cifs_sb); } -- 2.47.3