[GFS2] Patch to detect corrupt number of dir entries in leaf and/or inode blocks

This patch detects when the number of entries in a leaf block or inode
block (in the case of stuffed directories) is corrupt and informs the
user. It prevents us from running off the end of the array thats been
allocated for the sorting in this case,

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/dir.c

@@ -1262,9 +1262,10 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
 			      u64 leaf_no)
 {
 	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
 	struct buffer_head *bh;
 	struct gfs2_leaf *lf;
-	unsigned entries = 0;
+	unsigned entries = 0, entries2 = 0;
 	unsigned leaves = 0;
 	const struct gfs2_dirent **darr, *dent;
 	struct dirent_gather g;
@@ -1290,7 +1291,13 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
 		return 0;
 
 	error = -ENOMEM;
-	larr = vmalloc((leaves + entries) * sizeof(void *));
+	/*
+	 * The extra 99 entries are not normally used, but are a buffer
+	 * zone in case the number of entries in the leaf is corrupt.
+	 * 99 is the maximum number of entries that can fit in a single
+	 * leaf block.
+	 */
+	larr = vmalloc((leaves + entries + 99) * sizeof(void *));
 	if (!larr)
 		goto out;
 	darr = (const struct gfs2_dirent **)(larr + leaves);
@@ -1305,10 +1312,18 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
 		lf = (struct gfs2_leaf *)bh->b_data;
 		lfn = be64_to_cpu(lf->lf_next);
 		if (lf->lf_entries) {
+			entries2 += be16_to_cpu(lf->lf_entries);
 			dent = gfs2_dirent_scan(inode, bh->b_data, bh->b_size,
 						gfs2_dirent_gather, NULL, &g);
 			error = PTR_ERR(dent);
-			if (IS_ERR(dent)) {
+			if (IS_ERR(dent))
+				goto out_kfree;
+			if (entries2 != g.offset) {
+				fs_warn(sdp, "Number of entries corrupt in dir leaf %llu, "
+				        "entries2 (%u) != g.offset (%u)\n",
+					(u64)bh->b_blocknr, entries2, g.offset);
+					
+				error = -EIO;
 				goto out_kfree;
 			}
 			error = 0;
@@ -1318,6 +1333,7 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
 		}
 	} while(lfn);
 
+	BUG_ON(entries2 != entries);
 	error = do_filldir_main(ip, offset, opaque, filldir, darr,
 				entries, copied);
 out_kfree:
@@ -1401,6 +1417,7 @@ int gfs2_dir_read(struct inode *inode, u64 *offset, void *opaque,
 		  filldir_t filldir)
 {
 	struct gfs2_inode *dip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
 	struct dirent_gather g;
 	const struct gfs2_dirent **darr, *dent;
 	struct buffer_head *dibh;
@@ -1423,8 +1440,8 @@ int gfs2_dir_read(struct inode *inode, u64 *offset, void *opaque,
 		return error;
 
 	error = -ENOMEM;
-	darr = kmalloc(dip->i_di.di_entries * sizeof(struct gfs2_dirent *),
-		       GFP_KERNEL);
+	/* 96 is max number of dirents which can be stuffed into an inode */
+	darr = kmalloc(96 * sizeof(struct gfs2_dirent *), GFP_KERNEL);
 	if (darr) {
 		g.pdent = darr;
 		g.offset = 0;
@@ -1434,6 +1451,14 @@ int gfs2_dir_read(struct inode *inode, u64 *offset, void *opaque,
 			error = PTR_ERR(dent);
 			goto out;
 		}
+		if (dip->i_di.di_entries != g.offset) {
+			fs_warn(sdp, "Number of entries corrupt in dir %llu, "
+				"ip->i_di.di_entries (%u) != g.offset (%u)\n",
+				dip->i_num.no_addr, dip->i_di.di_entries,
+				g.offset);
+			error = -EIO;
+			goto out;
+		}
 		error = do_filldir_main(dip, offset, opaque, filldir, darr,
 					dip->i_di.di_entries, &copied);
 out: