From fe8715e1337a1bad5c49e165ab77c033c334efbc Mon Sep 17 00:00:00 2001

From: Qu Wenruo <wqu@suse.com>

Date: Mon, 20 Jul 2020 20:51:08 +0800

Subject: [PATCH 1/2] btrfs-progs: convert: prevent 32bit overflow for

 cctx->total_bytes

[BUG]

When convert is called on a 64GiB ext4 fs, it fails like this:

  $ btrfs-convert  /dev/loop0p1

  create btrfs filesystem:

          blocksize: 4096

          nodesize:  16384

          features:  extref, skinny-metadata (default)

          checksum:  crc32c

  creating ext2 image file

  ERROR: missing data block for bytenr 1048576

  ERROR: failed to create ext2_saved/image: -2

  WARNING: an error occurred during conversion, filesystem is partially created but not finalized and not mountable

Btrfs-convert also corrupts the source fs:

  $ LANG=C e2fsck /dev/loop0p1 -f

  e2fsck 1.45.6 (20-Mar-2020)

  Resize inode not valid.  Recreate<y>? yes

  Pass 1: Checking inodes, blocks, and sizes

  Deleted inode 3681 has zero dtime.  Fix<y>? yes

  Inodes that were part of a corrupted orphan linked list found.  Fix<y>? yes

  Inode 3744 was part of the orphaned inode list.  FIXED.

  Deleted inode 3745 has zero dtime.  Fix<y>? yes

  Inode 3747 has INLINE_DATA_FL flag on filesystem without inline data support.

  Clear<y>? yes

  ...

[CAUSE]

After some debugging, the first strange behavior is, the value of

cctx->total_bytes is 0 in ext2_open_fs().

It turns out that, the value assign for cctx->total_bytes could lead to

bit overflow for the unsigned int value.

And that 0 cctx->total_bytes leads to various problems for later free

space calculation.

For example, in calculate_available_space(), we use cctx->total_bytes to

ensure we won't create a data chunk beyond device end:

		cue_len = min(cctx->total_bytes - cur_off, cur_len);

If that cur_offset is also 0, we will create a cache_extent with 0 size,

which could cause a lot of problems for cache tree search.

[FIX]

Do manual casting for the multiply operation, so we could got a real u64

result.  The fix will be applied to all supported fses (ext* and

reiserfs).

Reported-by: Christian Zangl <coralllama@gmail.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

Signed-off-by: Qu Wenruo <wqu@suse.com>

Signed-off-by: David Sterba <dsterba@suse.com>

(cherry picked from commit 670a19828ad40004d05ad70cdd45d58008d3fb51)

---

 convert/main.c            | 1 +

 convert/source-ext2.c     | 2 +-

 convert/source-reiserfs.c | 2 +-

 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/convert/main.c b/convert/main.c

index 7709e9a6..df6a2ae3 100644

--- a/convert/main.c

+++ b/convert/main.c

@@ -1136,6 +1136,7 @@ static int do_convert(const char *devname, u32 convert_flags, u32 nodesize,

 	if (ret)

 		goto fail;

+	ASSERT(cctx.total_bytes);

 	blocksize = cctx.blocksize;

 	total_bytes = (u64)blocksize * (u64)cctx.block_count;

 	if (blocksize < 4096) {

diff --git a/convert/source-ext2.c b/convert/source-ext2.c

index f11ef651..d73684ef 100644

--- a/convert/source-ext2.c

+++ b/convert/source-ext2.c

@@ -87,7 +87,7 @@ static int ext2_open_fs(struct btrfs_convert_context *cctx, const char *name)

 	cctx->fs_data = ext2_fs;

 	cctx->blocksize = ext2_fs->blocksize;

 	cctx->block_count = ext2_fs->super->s_blocks_count;

-	cctx->total_bytes = ext2_fs->blocksize * ext2_fs->super->s_blocks_count;

+	cctx->total_bytes = (u64)ext2_fs->super->s_blocks_count * ext2_fs->blocksize;

 	cctx->volume_name = strndup((char *)ext2_fs->super->s_volume_name, 16);

 	cctx->first_data_block = ext2_fs->super->s_first_data_block;

 	cctx->inodes_count = ext2_fs->super->s_inodes_count;

diff --git a/convert/source-reiserfs.c b/convert/source-reiserfs.c

index 9fd6b9ab..3b4cb5ad 100644

--- a/convert/source-reiserfs.c

+++ b/convert/source-reiserfs.c

@@ -82,7 +82,7 @@ static int reiserfs_open_fs(struct btrfs_convert_context *cxt, const char *name)

 	cxt->fs_data = fs;

 	cxt->blocksize = fs->fs_blocksize;

 	cxt->block_count = get_sb_block_count(fs->fs_ondisk_sb);

-	cxt->total_bytes = cxt->blocksize * cxt->block_count;

+	cxt->total_bytes = (u64)cxt->block_count * cxt->blocksize;

 	cxt->volume_name = strndup(fs->fs_ondisk_sb->s_label, 16);

 	cxt->first_data_block = 0;

 	cxt->inodes_count = reiserfs_count_objectids(fs);

-- 

2.26.2