Commits
Qu Wenruo committed 314bfa473b6
btrfs: lzo: Add header length check to avoid potential out-of-bounds access James Harvey reported that some corrupted compressed extent data can lead to various kernel memory corruption. Such corrupted extent data belongs to inode with NODATASUM flags, thus data csum won't help us detecting such bug. If lucky enough, KASAN could catch it like: BUG: KASAN: slab-out-of-bounds in lzo_decompress_bio+0x384/0x7a0 [btrfs] Write of size 4096 at addr ffff8800606cb0f8 by task kworker/u16:0/2338 CPU: 3 PID: 2338 Comm: kworker/u16:0 Tainted: G O 4.17.0-rc5-custom+ #50 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Workqueue: btrfs-endio btrfs_endio_helper [btrfs] Call Trace: dump_stack+0xc2/0x16b print_address_description+0x6a/0x270 kasan_report+0x260/0x380 memcpy+0x34/0x50 lzo_decompress_bio+0x384/0x7a0 [btrfs] end_compressed_bio_read+0x99f/0x10b0 [btrfs] bio_endio+0x32e/0x640 normal_work_helper+0x15a/0xea0 [btrfs] process_one_work+0x7e3/0x1470 worker_thread+0x1b0/0x1170 kthread+0x2db/0x390 ret_from_fork+0x22/0x40 ... The offending compressed data has the following info: Header: length 32768 (looks completely valid) Segment 0 Header: length 3472882419 (obviously out of bounds) Then when handling segment 0, since it's over the current page, we need the copy the compressed data to temporary buffer in workspace, then such large size would trigger out-of-bounds memory access, screwing up the whole kernel. Fix it by adding extra checks on header and segment headers to ensure we won't access out-of-bounds, and even checks the decompressed data won't be out-of-bounds. Reported-by: James Harvey <jamespharvey20@gmail.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com> Reviewed-by: David Sterba <dsterba@suse.com> [ updated comments ] Signed-off-by: David Sterba <dsterba@suse.com>