From fe8715e1337a1bad5c49e165ab77c033c334efbc Mon Sep 17 00:00:00 2001 From: Qu Wenruo 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? yes Pass 1: Checking inodes, blocks, and sizes Deleted inode 3681 has zero dtime. Fix? yes Inodes that were part of a corrupted orphan linked list found. Fix? yes Inode 3744 was part of the orphaned inode list. FIXED. Deleted inode 3745 has zero dtime. Fix? yes Inode 3747 has INLINE_DATA_FL flag on filesystem without inline data support. Clear? 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 Reviewed-by: Nikolay Borisov Signed-off-by: Qu Wenruo Signed-off-by: David Sterba (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