[PATCH] ext2fs_zero_blocks: Avoid clearing more blocks than requested

[Theodore Ts'o <tytso@mit.edu>]

This could cause certain mke2fs feature combinations to result in the
initial blocks of the inode table getting wiped out when the journal
is created.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 lib/ext2fs/mkjournal.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/ext2fs/mkjournal.c b/lib/ext2fs/mkjournal.c
index ca8e733..e55dcbd 100644
--- a/lib/ext2fs/mkjournal.c
+++ b/lib/ext2fs/mkjournal.c
@@ -170,9 +170,11 @@ errcode_t ext2fs_zero_blocks(ext2_filsys fs, blk_t blk, int num,
 	/* OK, do the write loop */
 	j=0;
 	while (j < num) {
-		if (blk % STRIDE_LENGTH)
+		if (blk % STRIDE_LENGTH) {
 			count = STRIDE_LENGTH - (blk % STRIDE_LENGTH);
-		else {
+			if (count > (num - j))
+				count = num - j;
+		} else {
 			count = num - j;
 			if (count > STRIDE_LENGTH)
 				count = STRIDE_LENGTH;
-- 
1.5.6.rc3.1.g36b7.dirty