[PATCH 5.16 141/164] btrfs: prevent copying too big compressed lzo segment

Greg Kroah-Hartman
2022-02-28T18:12:10Z

From: Dāvis Mosāns <davispuh@gmail.com>

commit 741b23a970a79d5d3a1db2d64fa2c7b375a4febb upstream.

Compressed length can be corrupted to be a lot larger than memory
we have allocated for buffer.
This will cause memcpy in copy_compressed_segment to write outside
of allocated memory.

This mostly results in stuck read syscall but sometimes when using
btrfs send can get #GP

kernel: general protection fault, probably for non-canonical address 0x841551d5c1000: 0000 [#1] PREEMPT SMP NOPTI
kernel: CPU: 17 PID: 264 Comm: kworker/u256:7 Tainted: P OE 5.17.0-rc2-1 #12
kernel: Workqueue: btrfs-endio btrfs_work_helper [btrfs]
kernel: RIP: 0010:lzo_decompress_bio (./include/linux/fortify-string.h:225 fs/btrfs/lzo.c:322 fs/btrfs/lzo.c:394) btrfs
Code starting with the faulting instruction
===========================================
0:* 48 8b 06 mov (%rsi),%rax <-- trapping instruction
3: 48 8d 79 08 lea 0x8(%rcx),%rdi
7: 48 83 e7 f8 and $0xfffffffffffffff8,%rdi
b: 48 89 01 mov %rax,(%rcx)
e: 44 89 f0 mov %r14d,%eax
11: 48 8b 54 06 f8 mov -0x8(%rsi,%rax,1),%rdx
kernel: RSP: 0018:ffffb110812efd50 EFLAGS: 00010212
kernel: RAX: 0000000000001000 RBX: 000000009ca264c8 RCX: ffff98996e6d8ff8
kernel: RDX: 0000000000000064 RSI: 000841551d5c1000 RDI: ffffffff9500435d
kernel: RBP: ffff989a3be856c0 R08: 0000000000000000 R09: 0000000000000000
kernel: R10: 0000000000000000 R11: 0000000000001000 R12: ffff98996e6d8000
kernel: R13: 0000000000000008 R14: 0000000000001000 R15: 000841551d5c1000
kernel: FS: 0000000000000000(0000) GS:ffff98a09d640000(0000) knlGS:0000000000000000
kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
kernel: CR2: 00001e9f984d9ea8 CR3: 000000014971a000 CR4: 00000000003506e0
kernel: Call Trace:
kernel: <TASK>
kernel: end_compressed_bio_read (fs/btrfs/compression.c:104 fs/btrfs/compression.c:1363 fs/btrfs/compression.c:323) btrfs
kernel: end_workqueue_fn (fs/btrfs/disk-io.c:1923) btrfs
kernel: btrfs_work_helper (fs/btrfs/async-thread.c:326) btrfs
kernel: process_one_work (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:212 ./include/trace/events/workqueue.h:108 kernel/workqueue.c:2312)
kernel: worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2455)
kernel: ? process_one_work (kernel/workqueue.c:2397)
kernel: kthread (kernel/kthread.c:377)
kernel: ? kthread_complete_and_exit (kernel/kthread.c:332)
kernel: ret_from_fork (arch/x86/entry/entry_64.S:301)
kernel: </TASK>

CC: stable@vger.kernel.org # 4.9+
Signed-off-by: Dāvis Mosāns <davispuh@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/lzo.c | 11 +++++++++++
1 file changed, 11 insertions(+)

--- a/fs/btrfs/lzo.c
+++ b/fs/btrfs/lzo.c
@@ -380,6 +380,17 @@ int lzo_decompress_bio(struct list_head
kunmap(cur_page);
cur_in += LZO_LEN;

+ if (seg_len > lzo1x_worst_compress(PAGE_SIZE)) {
+ /*
+ * seg_len shouldn't be larger than we have allocated
+ * for workspace->cbuf
+ */
+ btrfs_err(fs_info, "unexpectedly large lzo segment len %u",
+ seg_len);
+ ret = -EIO;
+ goto out;
+ }
+
/* Copy the compressed segment payload into workspace */
copy_compressed_segment(cb, workspace->cbuf, seg_len, &cur_in);