High · published August 28, 2026
In the Linux kernel, the following vulnerability has been resolved:
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.