smb3: fix stat when special device file and mounted with modefromsid

commit 3c3317daef0afa0cd541fc9c1bfd6ce8bbf1129a upstream.

When mounting with modefromsid mount option, it was possible to
get the error on stat of a fifo or char or block device:
        "cannot stat <filename>: Operation not supported"

Special devices can be stored as reparse points by some servers
(e.g. Windows NFS server and when using the SMB3.1.1 POSIX
Extensions) but when the modefromsid mount option is used
the client attempts to get the ACL for the file which requires
opening with OPEN_REPARSE_POINT create option.

Signed-off-by: Steve French <stfrench@microsoft.com>
CC: Stable <stable@vger.kernel.org>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index bf94565312735bd2ee0d3fe56f136be247ab66b4..09e1cd320ee560c3f755a77465e1085950bf31bd 100644 (file)
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -3072,7 +3072,12 @@ get_smb2_acl_by_path(struct cifs_sb_info *cifs_sb,
        oparms.tcon = tcon;
        oparms.desired_access = READ_CONTROL;
        oparms.disposition = FILE_OPEN;
-       oparms.create_options = cifs_create_options(cifs_sb, 0);
+       /*
+        * When querying an ACL, even if the file is a symlink we want to open
+        * the source not the target, and so the protocol requires that the
+        * client specify this flag when opening a reparse point
+        */
+       oparms.create_options = cifs_create_options(cifs_sb, 0) | OPEN_REPARSE_POINT;
        oparms.fid = &fid;
        oparms.reconnect = false;