Fix loops over group descriptors to prevent 2**32-1 block number overflows

For loops iterating over all group descriptors, consistently define
first_block and last_block in a way that they are inclusive of the
range, and do not overflow.

Previously on the last block group we did a test of <= first +
dec_blocks; this would actually wrap back to 0 for a total block count
of 2^32-1

Also add handling of last block group which may be smaller.

Signed-off-by: Eric Sandeen <esandeen@redhat.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/e2fsck/pass1b.c b/e2fsck/pass1b.c
index a9640ffa..cec60cf4 100644
--- a/e2fsck/pass1b.c
+++ b/e2fsck/pass1b.c
@@ -779,16 +779,16 @@ errout:
 static int check_if_fs_block(e2fsck_t ctx, blk_t test_block)
 {
 	ext2_filsys fs = ctx->fs;
-	blk_t	block;
+	blk_t	first_block;
 	dgrp_t	i;
 	
-	block = fs->super->s_first_data_block;
+	first_block = fs->super->s_first_data_block;
 	for (i = 0; i < fs->group_desc_count; i++) {
 
-		/* Check superblocks/block group descriptros */
+		/* Check superblocks/block group descriptors */
 		if (ext2fs_bg_has_super(fs, i)) {
-			if (test_block >= block &&
-			    (test_block <= block + fs->desc_blocks))
+			if (test_block >= first_block &&
+			    (test_block <= first_block + fs->desc_blocks))
 				return 1;
 		}
 		
@@ -804,7 +804,7 @@ static int check_if_fs_block(e2fsck_t ctx, blk_t test_block)
 		    (test_block == fs->group_desc[i].bg_inode_bitmap))
 			return 1;
 		
-		block += fs->super->s_blocks_per_group;
+		first_block += fs->super->s_blocks_per_group;
 	}
 	return 0;
 }