Fix potential 2**32-1 overflow problems by ext2fs_div_ceil()
Add a new function, ext2fs_div_ceil(), which correctly calculates a division
of two unsigned integer where the result is always rounded up the next
largest integer. This is used everywhere where we might have
previously caused an overflow when the number of blocks
or inodes is too close to 2**32-1.
Based on patches from Eric Sandeen, but generalized to use this new function
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Eric Sandeen <esandeen@redhat.com>
diff --git a/lib/ext2fs/initialize.c b/lib/ext2fs/initialize.c
index 05ba8c8..6b476d9 100644
--- a/lib/ext2fs/initialize.c
+++ b/lib/ext2fs/initialize.c
@@ -77,8 +77,8 @@
*/
if (sb->s_blocks_count < max_blocks / 1024)
max_blocks = sb->s_blocks_count * 1024;
- rsv_groups = (max_blocks - sb->s_first_data_block + bpg - 1) / bpg;
- rsv_gdb = (rsv_groups + gdpb - 1) / gdpb - fs->desc_blocks;
+ rsv_groups = ext2fs_div_ceil(max_blocks - sb->s_first_data_block, bpg);
+ rsv_gdb = ext2fs_div_ceil(rsv_groups, gdpb) - fs->desc_blocks;
if (rsv_gdb > EXT2_ADDR_PER_BLOCK(sb))
rsv_gdb = EXT2_ADDR_PER_BLOCK(sb);
#ifdef RES_GDT_DEBUG
@@ -205,17 +205,15 @@
}
retry:
- fs->group_desc_count = (super->s_blocks_count -
- super->s_first_data_block +
- EXT2_BLOCKS_PER_GROUP(super) - 1)
- / EXT2_BLOCKS_PER_GROUP(super);
+ fs->group_desc_count = ext2fs_div_ceil(super->s_blocks_count -
+ super->s_first_data_block,
+ EXT2_BLOCKS_PER_GROUP(super));
if (fs->group_desc_count == 0) {
retval = EXT2_ET_TOOSMALL;
goto cleanup;
}
- fs->desc_blocks = (fs->group_desc_count +
- EXT2_DESC_PER_BLOCK(super) - 1)
- / EXT2_DESC_PER_BLOCK(super);
+ fs->desc_blocks = ext2fs_div_ceil(fs->group_desc_count,
+ EXT2_DESC_PER_BLOCK(super));
i = fs->blocksize >= 4096 ? 1 : 4096 / fs->blocksize;
set_field(s_inodes_count, super->s_blocks_count / i);
@@ -233,8 +231,7 @@
* should be. But make sure that we don't allocate more than
* one bitmap's worth of inodes each group.
*/
- ipg = (super->s_inodes_count + fs->group_desc_count - 1) /
- fs->group_desc_count;
+ ipg = ext2fs_div_ceil(super->s_inodes_count, fs->group_desc_count);
if (ipg > fs->blocksize * 8) {
if (super->s_blocks_per_group >= 256) {
/* Try again with slightly different parameters */