The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 741b23a970a79d5d3a1db2d64fa2c7b375a4febb Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?D=C4=81vis=20Mos=C4=81ns?= davispuh@gmail.com Date: Wed, 2 Feb 2022 23:44:55 +0200 Subject: [PATCH] btrfs: prevent copying too big compressed lzo segment MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

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

diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c index 0fb90cbe7669..e6e28a9c7987 100644 --- a/fs/btrfs/lzo.c +++ b/fs/btrfs/lzo.c @@ -380,6 +380,17 @@ int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb) 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);