cifs: Handle extended attribute name cifs_acl to generate cifs acl blob (try #4)

Add extended attribute name system.cifs_acl

Get/generate cifs/ntfs acl blob and hand over to the invoker however
it wants to parse/process it under experimental configurable option CIFS_ACL.

Do not get CIFS/NTFS ACL for xattr for attribute system.posix_acl_access

Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/Kconfig

@@ -144,6 +144,13 @@ config CIFS_FSCACHE
 	    to be cached locally on disk through the general filesystem cache
 	    manager. If unsure, say N.
 
+config CIFS_ACL
+	  bool "Provide CIFS ACL support (EXPERIMENTAL)"
+	  depends on EXPERIMENTAL && CIFS_XATTR
+	  help
+	    Allows to fetch CIFS/NTFS ACL from the server.  The DACL blob
+	    is handed over to the application/caller.
+
 config CIFS_EXPERIMENTAL
 	  bool "CIFS Experimental Features (EXPERIMENTAL)"
 	  depends on CIFS && EXPERIMENTAL

fs/cifs/cifsacl.c

@@ -608,7 +608,7 @@ static struct cifs_ntsd *get_cifs_acl_by_path(struct cifs_sb_info *cifs_sb,
 }
 
 /* Retrieve an ACL from the server */
-static struct cifs_ntsd *get_cifs_acl(struct cifs_sb_info *cifs_sb,
+struct cifs_ntsd *get_cifs_acl(struct cifs_sb_info *cifs_sb,
 				      struct inode *inode, const char *path,
 				      u32 *pacllen)
 {

fs/cifs/cifsproto.h

@@ -134,6 +134,8 @@ extern int cifs_acl_to_fattr(struct cifs_sb_info *cifs_sb,
 			      struct cifs_fattr *fattr, struct inode *inode,
 			      const char *path, const __u16 *pfid);
 extern int mode_to_cifs_acl(struct inode *inode, const char *path, __u64);
+extern struct cifs_ntsd *get_cifs_acl(struct cifs_sb_info *, struct inode *,
+					const char *, u32 *);
 
 extern int cifs_mount(struct super_block *, struct cifs_sb_info *, char *,
 			const char *);

fs/cifs/xattr.c

@@ -30,10 +30,11 @@
 
 #define MAX_EA_VALUE_SIZE 65535
 #define CIFS_XATTR_DOS_ATTRIB "user.DosAttrib"
+#define CIFS_XATTR_CIFS_ACL "system.cifs_acl"
 #define CIFS_XATTR_USER_PREFIX "user."
 #define CIFS_XATTR_SYSTEM_PREFIX "system."
 #define CIFS_XATTR_OS2_PREFIX "os2."
-#define CIFS_XATTR_SECURITY_PREFIX ".security"
+#define CIFS_XATTR_SECURITY_PREFIX "security."
 #define CIFS_XATTR_TRUSTED_PREFIX "trusted."
 #define XATTR_TRUSTED_PREFIX_LEN  8
 #define XATTR_SECURITY_PREFIX_LEN 9
@@ -277,29 +278,8 @@ ssize_t cifs_getxattr(struct dentry *direntry, const char *ea_name,
 				cifs_sb->local_nls,
 				cifs_sb->mnt_cifs_flags &
 					CIFS_MOUNT_MAP_SPECIAL_CHR);
-#ifdef CONFIG_CIFS_EXPERIMENTAL
-		else if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL) {
-			__u16 fid;
-			int oplock = 0;
-			struct cifs_ntsd *pacl = NULL;
-			__u32 buflen = 0;
-			if (experimEnabled)
-				rc = CIFSSMBOpen(xid, pTcon, full_path,
-					FILE_OPEN, GENERIC_READ, 0, &fid,
-					&oplock, NULL, cifs_sb->local_nls,
-					cifs_sb->mnt_cifs_flags &
-					CIFS_MOUNT_MAP_SPECIAL_CHR);
-			/* else rc is EOPNOTSUPP from above */
-
-			if (rc == 0) {
-				rc = CIFSSMBGetCIFSACL(xid, pTcon, fid, &pacl,
-						      &buflen);
-				CIFSSMBClose(xid, pTcon, fid);
-			}
-		}
-#endif /* EXPERIMENTAL */
 #else
-		cFYI(1, "query POSIX ACL not supported yet");
+		cFYI(1, "Query POSIX ACL not supported yet");
 #endif /* CONFIG_CIFS_POSIX */
 	} else if (strncmp(ea_name, POSIX_ACL_XATTR_DEFAULT,
 			  strlen(POSIX_ACL_XATTR_DEFAULT)) == 0) {
@@ -311,8 +291,33 @@ ssize_t cifs_getxattr(struct dentry *direntry, const char *ea_name,
 				cifs_sb->mnt_cifs_flags &
 					CIFS_MOUNT_MAP_SPECIAL_CHR);
 #else
-		cFYI(1, "query POSIX default ACL not supported yet");
-#endif
+		cFYI(1, "Query POSIX default ACL not supported yet");
+#endif /* CONFIG_CIFS_POSIX */
+	} else if (strncmp(ea_name, CIFS_XATTR_CIFS_ACL,
+				strlen(CIFS_XATTR_CIFS_ACL)) == 0) {
+#ifdef CONFIG_CIFS_ACL
+			u32 acllen;
+			struct cifs_ntsd *pacl;
+
+			pacl = get_cifs_acl(cifs_sb, direntry->d_inode,
+						full_path, &acllen);
+			if (IS_ERR(pacl)) {
+				rc = PTR_ERR(pacl);
+				cERROR(1, "%s: error %zd getting sec desc",
+						__func__, rc);
+			} else {
+				if (ea_value) {
+					if (acllen > buf_size)
+						acllen = -ERANGE;
+					else
+						memcpy(ea_value, pacl, acllen);
+				}
+				rc = acllen;
+				kfree(pacl);
+			}
+#else
+		cFYI(1, "Query CIFS ACL not supported yet");
+#endif /* CONFIG_CIFS_ACL */
 	} else if (strncmp(ea_name,
 		  CIFS_XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) == 0) {
 		cFYI(1, "Trusted xattr namespace not supported yet");