[Midnightbsd-cvs] src [7931] trunk/sys/fs/nfsclient/nfs_clbio.c: improve handling of uiomove(9) errors for the NFS client.

[laffer1 at midnightbsd.org]

Revision: 7931
          http://svnweb.midnightbsd.org/src/?rev=7931
Author:   laffer1
Date:     2016-09-14 17:11:09 -0400 (Wed, 14 Sep 2016)
Log Message:
-----------
improve handling of uiomove(9) errors for the NFS client.

Modified Paths:
--------------
    trunk/sys/fs/nfsclient/nfs_clbio.c

Modified: trunk/sys/fs/nfsclient/nfs_clbio.c
===================================================================
--- trunk/sys/fs/nfsclient/nfs_clbio.c	2016-09-14 21:09:43 UTC (rev 7930)
+++ trunk/sys/fs/nfsclient/nfs_clbio.c	2016-09-14 21:11:09 UTC (rev 7931)
@@ -873,8 +873,9 @@
 	struct nfsmount *nmp = VFSTONFS(vp->v_mount);
 	daddr_t lbn;
 	int bcount;
-	int n, on, error = 0;
-	off_t tmp_off;
+	int bp_cached, n, on, error = 0;
+	size_t orig_resid, local_resid;
+	off_t orig_size, tmp_off;
 
 	KASSERT(uio->uio_rw == UIO_WRITE, ("ncl_write mode"));
 	KASSERT(uio->uio_segflg != UIO_USERSPACE || uio->uio_td == curthread,
@@ -926,6 +927,11 @@
 			mtx_unlock(&np->n_mtx);
 	}
 
+	orig_resid = uio->uio_resid;
+	mtx_lock(&np->n_mtx);
+	orig_size = np->n_size;
+	mtx_unlock(&np->n_mtx);
+
 	/*
 	 * If IO_APPEND then load uio_offset.  We restart here if we cannot
 	 * get the append lock.
@@ -1103,7 +1109,10 @@
 		 * normally.
 		 */
 
+		bp_cached = 1;
 		if (on == 0 && n == bcount) {
+			if ((bp->b_flags & B_CACHE) == 0)
+				bp_cached = 0;
 			bp->b_flags |= B_CACHE;
 			bp->b_flags &= ~B_INVAL;
 			bp->b_ioflags &= ~BIO_ERROR;
@@ -1169,8 +1178,24 @@
 			goto again;
 		}
 
+		local_resid = uio->uio_resid;
 		error = uiomove((char *)bp->b_data + on, n, uio);
 
+		if (error != 0 && !bp_cached) {
+			/*
+			 * This block has no other content then what
+			 * possibly was written by the faulty uiomove.
+			 * Release it, forgetting the data pages, to
+			 * prevent the leak of uninitialized data to
+			 * usermode.
+			 */
+			bp->b_ioflags |= BIO_ERROR;
+			brelse(bp);
+			uio->uio_offset -= local_resid - uio->uio_resid;
+			uio->uio_resid = local_resid;
+			break;
+		}
+
 		/*
 		 * Since this block is being modified, it must be written
 		 * again and not just committed.  Since write clustering does
@@ -1179,17 +1204,18 @@
 		 */
 		bp->b_flags &= ~(B_NEEDCOMMIT | B_CLUSTEROK);
 
-		if (error) {
-			bp->b_ioflags |= BIO_ERROR;
-			brelse(bp);
-			break;
-		}
+		/*
+		 * Get the partial update on the progress made from
+		 * uiomove, if an error occured.
+		 */
+		if (error != 0)
+			n = local_resid - uio->uio_resid;
 
 		/*
 		 * Only update dirtyoff/dirtyend if not a degenerate
 		 * condition.
 		 */
-		if (n) {
+		if (n > 0) {
 			if (bp->b_dirtyend > 0) {
 				bp->b_dirtyoff = min(on, bp->b_dirtyoff);
 				bp->b_dirtyend = max((on + n), bp->b_dirtyend);
@@ -1218,8 +1244,22 @@
 		} else {
 			bdwrite(bp);
 		}
+
+		if (error != 0)
+			break;
 	} while (uio->uio_resid > 0 && n > 0);
 
+	if (error != 0) {
+		if (ioflag & IO_UNIT) {
+			VATTR_NULL(&vattr);
+			vattr.va_size = orig_size;
+			/* IO_SYNC is handled implicitely */
+			(void)VOP_SETATTR(vp, &vattr, cred);
+			uio->uio_offset -= orig_resid - uio->uio_resid;
+			uio->uio_resid = orig_resid;
+		}
+	}
+
 	return (error);
 }