From: Qu Wenruo <wqu@xxxxxxxx> commit 3777369ff1518b579560611a0d0c33f930154f64 upstream. [BUG] There is a bug report that a bitflip in the transid part of an extent buffer makes btrfs to reject certain tree blocks: BTRFS error (device dm-0): parent transid verify failed on 1382301696 wanted 262166 found 22 [CAUSE] Note the failed transid check, hex(262166) = 0x40016, while hex(22) = 0x16. It's an obvious bitflip. Furthermore, the reporter also confirmed the bitflip is from the hardware, so it's a real hardware caused bitflip, and such problem can not be detected by the existing tree-checker framework. As tree-checker can only verify the content inside one tree block, while generation of a tree block can only be verified against its parent. So such problem remain undetected. [FIX] Although tree-checker can not verify it at write-time, we still have a quick (but not the most accurate) way to catch such obvious corruption. Function csum_one_extent_buffer() is called before we submit metadata write. Thus it means, all the extent buffer passed in should be dirty tree blocks, and should be newer than last committed transaction. Using that we can catch the above bitflip. Although it's not a perfect solution, as if the corrupted generation is higher than the correct value, we have no way to catch it at all. Reported-by: Christoph Anton Mitterer <calestyo@xxxxxxxxxxxx> Link: https://lore.kernel.org/linux-btrfs/2dfcbc130c55cc6fd067b93752e90bd2b079baca.camel@xxxxxxxxxxxx/ CC: stable@xxxxxxxxxxxxxxx # 5.15+ Signed-off-by: Qu Wenruo <wqu@sus,ree.com> Reviewed-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/btrfs/disk-io.c | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -441,17 +441,31 @@ static int csum_one_extent_buffer(struct else ret = btrfs_check_leaf_full(eb); - if (ret < 0) { - btrfs_print_tree(eb, 0); + if (ret < 0) + goto error; + + /* + * Also check the generation, the eb reached here must be newer than + * last committed. Or something seriously wrong happened. + */ + if (unlikely(btrfs_header_generation(eb) <= fs_info->last_trans_committed)) { + ret = -EUCLEAN; btrfs_err(fs_info, - "block=%llu write time tree block corruption detected", - eb->start); - WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG)); - return ret; + "block=%llu bad generation, have %llu expect > %llu", + eb->start, btrfs_header_generation(eb), + fs_info->last_trans_committed); + goto error; } write_extent_buffer(eb, result, 0, fs_info->csum_size); return 0; + +error: + btrfs_print_tree(eb, 0); + btrfs_err(fs_info, "block=%llu write time tree block corruption detected", + eb->start); + WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG)); + return ret; } /* Checksum all dirty extent buffers in one bio_vec */
