linux-ext4 - [PATCH 3/6] e2fsck: Fix incorrect bbitmap checksum failure caused by integer overflow

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Date:	Wed, 28 Aug 2013 17:44:04 -0700
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	tytso@....edu, darrick.wong@...cle.com
Cc:	linux-ext4@...r.kernel.org
Subject: [PATCH 3/6] e2fsck: Fix incorrect bbitmap checksum failure caused by
 integer overflow

On a filesystem with more than 2^32 blocks, the block group checksum test will
fail because "i" (the group number) is a 32-bit quantity that is used to
calculate the group's block bitmap block number.  Unfortunately, "i" is not
automatically promoted to 64-bit for this calculation and overflows.  When this
happens, e2fsck will incorrectly report bitmap checksum errors.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
 e2fsck/pass5.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/e2fsck/pass5.c b/e2fsck/pass5.c
index 51e4683..0fe7045 100644
--- a/e2fsck/pass5.c
+++ b/e2fsck/pass5.c
@@ -168,7 +168,7 @@ static void check_block_bitmap_checksum(e2fsck_t ctx)

 		blk_itr = EXT2FS_B2C(ctx->fs,
 				     ctx->fs->super->s_first_data_block) +
-			  (i * (nbytes << 3));
+			  ((blk64_t)i * (nbytes << 3));
 		retval = ext2fs_get_block_bitmap_range2(ctx->fs->block_map,
 							blk_itr, nbytes << 3,
 							buf);

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