Re: [PATCH v2] fstests: btrfs: a new test case to verify scrub and rescue=idatacsums

Filipe Manana
2025-05-12T11:17:27Z

On Mon, May 12, 2025 at 10:40 AM Qu Wenruo <wqu@suse.com> wrote:
>
> There is a kernel bug report that scrub will trigger a NULL pointer
> dereference when rescue=idatacsums mount option is provided.
>
> Add a test case for such situation, to verify kernel can gracefully
> reject scrub when there is no csum tree.
>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

Reviewed-by: Filipe Manana <fdmanana@suse.com>

Looks good now, thanks.

> ---
> Changelog:
> v2:
> - Strictly require the scrub to fail
> Suggested by Filipe
> ---
> tests/btrfs/336 | 35 +++++++++++++++++++++++++++++++++++
> tests/btrfs/336.out | 2 ++
> 2 files changed, 37 insertions(+)
> create mode 100755 tests/btrfs/336
> create mode 100644 tests/btrfs/336.out
>
> diff --git a/tests/btrfs/336 b/tests/btrfs/336
> new file mode 100755
> index 00000000..f6691bae
> --- /dev/null
> +++ b/tests/btrfs/336
> @@ -0,0 +1,35 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (C) 2025 SUSE Linux Products GmbH. All Rights Reserved.
> +#
> +# FS QA Test 336
> +#
> +# Make sure read-only scrub won't cause NULL pointer dereference with
> +# rescue=idatacsums mount option
> +#
> +. ./common/preamble
> +_begin_fstest auto scrub quick
> +
> +_fixed_by_kernel_commit 6aecd91a5c5b \
> + "btrfs: avoid NULL pointer dereference if no valid extent tree"
> +
> +_require_scratch
> +_scratch_mkfs >> $seqres.full
> +
> +_try_scratch_mount "-o ro,rescue=ignoredatacsums" > /dev/null 2>&1 ||
> + _notrun "rescue=ignoredatacsums mount option not supported"
> +
> +# For unpatched kernel this will cause NULL pointer dereference and crash the kernel.
> +$BTRFS_UTIL_PROG scrub start -Br $SCRATCH_MNT >> $seqres.full 2>&1
> +# For patched kernel scrub will be gracefully rejected.
> +if [ $? -eq 0 ]; then
> + echo "read-only scrub should fail but didn't"
> +fi
> +
> +_scratch_unmount
> +
> +echo "Silence is golden"
> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/btrfs/336.out b/tests/btrfs/336.out
> new file mode 100644
> index 00000000..9263628e
> --- /dev/null
> +++ b/tests/btrfs/336.out
> @@ -0,0 +1,2 @@
> +QA output created by 336
> +Silence is golden
> --
> 2.47.1
>
>