btrfs: lzo: reject compressed segment that overflows the compressed input

lzo_decompress_bio() validates each on-disk segment length seg_len only
against the workspace cbuf size, not against the compressed input size
(compressed_len, the total folio bytes of the bio).  A crafted extent can
carry a segment whose seg_len passes the cbuf check but runs past the end
of the bio, so copy_compressed_segment() walks off the last folio:
get_current_folio() then returns the NULL folio from bio_next_folio(), and
with CONFIG_BTRFS_ASSERT disabled (default) folio_size(NULL) faults.

 BUG: KASAN: null-ptr-deref in lzo_decompress_bio (fs/btrfs/lzo.c:383)
 Read of size 8 at addr 0000000000000000 by task kworker/u8:1/29
 Workqueue: btrfs-endio simple_end_io_work
  kasan_report (mm/kasan/report.c:590)
  lzo_decompress_bio (fs/btrfs/lzo.c:383)
  end_bbio_compressed_read (fs/btrfs/compression.c:1065)
  btrfs_bio_end_io (fs/btrfs/bio.c:135)
  btrfs_check_read_bio (fs/btrfs/bio.c:180 fs/btrfs/bio.c:285)
  simple_end_io_work
  process_one_work
  worker_thread

Reject any segment whose payload would extend beyond compressed_len before
copying it, treating it as corruption like the other on-disk validation
failures in this function.

Reported-by: Xiang Mei <xmei5@asu.edu>
Fixes: a6e66e6f8c1b ("btrfs: rework lzo_decompress_bio() to make it subpage compatible")
Assisted-by: Claude:claude-opus-4-8
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>

0 files changed, 0 insertions, 0 deletions