PERFORCE change 163674 for review

[Robert Watson]

http://perforce.freebsd.org/chv.cgi?CH=163674

Change 163674 by rwatson at rwatson_freebsd_capabilities on 2009/06/06 22:40:45

	Complete merge of new file descriptor referencing and locking
	into the capabilities version of _fget().  Improve ifdefing.

Affected files ...

.. //depot/projects/trustedbsd/capabilities/src/sys/kern/kern_descrip.c#23 edit

Differences ...

==== //depot/projects/trustedbsd/capabilities/src/sys/kern/kern_descrip.c#23 (text+ko) ====

@@ -2155,7 +2155,10 @@
 {
 	struct filedesc *fdp;
 	struct file *fp;
+#ifdef CAPABILITIES
+	struct file *fp_fromcap;
 	int error;
+#endif
 
 	/*
 	 * Validate the file descriptor number and find the struct file.
@@ -2170,6 +2173,7 @@
 		return (EBADF);
 	}
 
+#ifdef CAPABILITIES
 	/*
 	 * If a capability has been requested, return the capability
 	 * directly.  Otherwise, check capability rights, extract the
@@ -2177,30 +2181,40 @@
 	 */
 	if (fget_flags & FGET_GETCAP) {
 		if (fp->f_type != DTYPE_CAPABILITY) {
-			FILEDESC_SUNLOCK(fdp);
+			fdrop(fp, td);
 			return (EINVAL);
 		}
 	} else {
 		/*
 		 * If a capability hasn't been requested, then validate the
-		 * capability and find the underlying object.  From now on
-		 * 'fp' refers to the actual object of interest.
+		 * capability and find the underlying object.
 		 */
 		if (maxprotp != NULL)
-			error = cap_fextract_mmap(fp, rights, maxprotp, &fp);
+			error = cap_fextract_mmap(fp, rights, maxprotp,
+			    &fp_fromcap);
 		else
-			error = cap_fextract(fp, rights, &fp);
+			error = cap_fextract(fp, rights, &fp_fromcap);
 		if (error) {
-			FILEDESC_SUNLOCK(fdp);
+			fdrop(fp, td);
 			return (error);
 		}
 
+		/*
+		 * Hold the new file descriptor and drop the capability file
+		 * descriptor; after this point fp refers to the new object.
+		 */
+		fhold(fp_fromcap);
+		fdrop(fp, td);
+		fp = fp_fromcap;
+#endif
 		if ((flags == FREAD && (fp->f_flag & FREAD) == 0) ||
 		    (flags == FWRITE && (fp->f_flag & FWRITE) == 0)) {
 			fdrop(fp, td);
 			return (EBADF);
 		}
+#ifdef CAPABILITIES
 	}
+#endif
 	*fpp = fp;
 	return (0);
 }
@@ -2224,7 +2238,7 @@
 fget_read(struct thread *td, int fd, cap_rights_t rights, struct file **fpp)
 {
 
-	return(_fget(td, fd, fpp, FWRITE, rights, NULL, 0));
+	return(_fget(td, fd, fpp, FREAD, rights, NULL, 0));
 }
 
 int