Re: struct file reference at VFS level

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

On Sun, Apr 24, 2016 at 07:11:37PM +0000, David Holland wrote:
> Since you said fuse has a way to do that but it doesn't work for our
> fuse, I guess the right way forward is to make it work in our fuse.
> What's required? Just send an arbitrary ID associated with the open
> through puffs to userland?

Here is the first part: a MNT_FILECRED mount option that cause
the struct file to be attached to VOP credentials. It builds but
I have not yet tested, as I need the second part in PUFFS for that.


Index: sys/sys/fstypes.h
===================================================================
RCS file: /cvsroot/src/sys/sys/fstypes.h,v
retrieving revision 1.33
diff -U4 -r1.33 fstypes.h
--- sys/sys/fstypes.h	6 May 2015 15:57:08 -0000	1.33
+++ sys/sys/fstypes.h	27 Apr 2016 15:54:05 -0000
@@ -79,12 +79,11 @@
  *
  * Unmount uses MNT_FORCE flag.
  *
  * Note that all mount flags are listed here.  if you need to add one, take
- * one of the __MNT_UNUSED flags.
+ * one of the __MNT_UNUSED flags (none available currently, sorry)
  */
 
-#define	__MNT_UNUSED1	0x00200000
 
 #define	MNT_RDONLY	0x00000001	/* read only filesystem */
 #define	MNT_SYNCHRONOUS	0x00000002	/* file system written synchronously */
 #define	MNT_NOEXEC	0x00000004	/* can't exec from filesystem */
@@ -94,8 +93,9 @@
 #define	MNT_ASYNC	0x00000040	/* file system written asynchronously */
 #define	MNT_NOCOREDUMP	0x00008000	/* don't write core dumps to this FS */
 #define	MNT_RELATIME	0x00020000	/* only update access time if mod/ch */
 #define	MNT_IGNORE	0x00100000	/* don't show entry in df */
+#define	MNT_FILECRED	0x00200000	/* provide file_t in VFS ops creds */
 #define	MNT_DISCARD	0x00800000	/* use DISCARD/TRIM if supported */
 #define	MNT_EXTATTR	0x01000000	/* enable extended attributes */
 #define	MNT_LOG		0x02000000	/* Use logging */
 #define	MNT_NOATIME	0x04000000	/* Never update access times in fs */
Index: sys/sys/kauth.h
===================================================================
RCS file: /cvsroot/src/sys/sys/kauth.h,v
retrieving revision 1.73
diff -U4 -r1.73 kauth.h
--- sys/sys/kauth.h	6 Oct 2015 22:13:39 -0000	1.73
+++ sys/sys/kauth.h	27 Apr 2016 15:54:05 -0000
@@ -85,8 +85,12 @@
 	specificdata_reference cr_sd;	/* specific data */
 };
 #endif
 
+#ifdef _KERNEL
+extern kauth_key_t kauth_filecred_key;;
+#endif
+
 /*
  * Possible return values for a listener.
  */
 #define	KAUTH_RESULT_ALLOW	0	/* allow access */
Index: sys/secmodel/secmodel.c
===================================================================
RCS file: /cvsroot/src/sys/secmodel/secmodel.c,v
retrieving revision 1.2
diff -U4 -r1.2 secmodel.c
--- sys/secmodel/secmodel.c	4 Nov 2014 16:01:58 -0000	1.2
+++ sys/secmodel/secmodel.c	27 Apr 2016 15:54:05 -0000
@@ -37,8 +37,11 @@
 #include <sys/rwlock.h>
 #include <secmodel/secmodel.h>
 #include <prop/proplib.h>
 
+/* kauth key for MNT_FILECRED mount option */
+kauth_key_t kauth_filecred_key;
+
 /* List of secmodels, parameters, and lock. */
 static LIST_HEAD(, secmodel_descr) secmodels =
     LIST_HEAD_INITIALIZER(secmodels);
 static unsigned int secmodel_copy_cred_on_fork = false;
@@ -61,8 +64,10 @@
 
 	rw_init(&secmodels_lock);
 
 	secmodel_copy_cred_on_fork = false;
+
+	(void)kauth_register_key(NULL, &kauth_filecred_key);
 }
 
 /*
  * Register a new secmodel.
Index: sys/kern/vfs_syscalls.c
===================================================================
RCS file: /cvsroot/src/sys/kern/vfs_syscalls.c,v
retrieving revision 1.504
diff -U4 -r1.504 vfs_syscalls.c
--- sys/kern/vfs_syscalls.c	28 Nov 2015 15:26:29 -0000	1.504
+++ sys/kern/vfs_syscalls.c	27 Apr 2016 15:54:05 -0000
@@ -218,8 +218,18 @@
 	fp->f_type = DTYPE_VNODE;
 	fp->f_ops = &vnops;
 	fp->f_vnode = vp;
 
+	if (vp->v_mount->mnt_flag & MNT_FILECRED) {
+		kauth_cred_t cred;
+
+		cred = kauth_cred_dup(fp->f_cred);
+		kauth_cred_free(fp->f_cred);
+		fp->f_cred = cred;
+
+		kauth_cred_setdata(cred, kauth_filecred_key, fp);
+	}
+
 	if (flags & (O_EXLOCK | O_SHLOCK)) {
 		struct flock lf;
 		int type;
 

-- 
Emmanuel Dreyfus
manu%netbsd.org@localhost