Re: [PATCH v5] ext4: Regression test of ext4_lblk_t overflow

[Baokun Li <libaokun1@huawei.com>]

On 2023/12/9 13:49, Zorro Lang wrote:
> On Fri, Nov 24, 2023 at 07:53:56PM +0800, Baokun Li wrote:
>> Append writes to a file with logical block numbers close to 0xffffffff and
>> observe if a kernel crash is caused by ext4_lblk_t overflow triggering
>> BUG_ON at ext4_mb_new_inode_pa(). This is a regression test for commit
>> bc056e7163ac ("ext4: fix BUG in ext4_mb_new_inode_pa() due to overflow")
>>
>> Signed-off-by: Baokun Li <libaokun1@huawei.com>
>> ---
>> V1->V2:
>> 	Changes to make the use case more generic, not just for testing
>> 	ext4.(ext4 and xfs have been tested)
>> V2->V3:
>> 	Clean up the code and remove hardcoding.
>> V3->V4:
>> 	Correct the description and modify finsert related code to
>> 	make the test case easier to understand.
>> V4->V5:
>> 	Modify the image size to 80M.
>> 	Modify the space reserved in the file to 2M.
>> 	Now the test case can trigger the original problem at ext4
>> 	1k,4k,64k block size.
>>
>>   tests/generic/737     | 54 +++++++++++++++++++++++++++++++++++++++++++
>>   tests/generic/737.out |  2 ++
>>   2 files changed, 56 insertions(+)
>>   create mode 100755 tests/generic/737
>>   create mode 100644 tests/generic/737.out
>>
>> diff --git a/tests/generic/737 b/tests/generic/737
>> new file mode 100755
>> index 00000000..b4bf33e4
>> --- /dev/null
>> +++ b/tests/generic/737
>> @@ -0,0 +1,54 @@
>> +#! /bin/bash
>> +# SPDX-License-Identifier: GPL-2.0
>> +# Copyright (c) 2023 HUAWEI.  All Rights Reserved.
>> +#
>> +# FS QA Test No. 737
>> +#
>> +# Append writes to a file with logical block numbers close to 0xffffffff
>> +# and observe if a kernel crash is caused by ext4_lblk_t overflow triggering
>> +# BUG_ON at ext4_mb_new_inode_pa(). This is a regression test for commit
>> +# bc056e7163ac ("ext4: fix BUG in ext4_mb_new_inode_pa() due to overflow")
>> +#
>> +. ./common/preamble
>> +. ./common/populate
>> +_begin_fstest auto quick insert prealloc
>> +
>> +# real QA test starts here
>> +[[ "$FSTYP" =~ ext* ]] && _fixed_by_kernel_commit bc056e7163ac \
> I just noticed this regex, I think the "ext*" matches "ex", "ext", "extxxx". So
> if FSTYP=exfat, then it will matchi the "ext*".
>
> It's better to be "ext.*" or "ext.+" or "ext[0-9]+". I'll change it when I
> merge it.
Okay. Thanks a lot!
>> +	"ext4: fix BUG in ext4_mb_new_inode_pa() due to overflow"
>> +
>> +_require_odirect
>> +_require_xfs_io_command "falloc"
>> +_require_xfs_io_command "finsert"
>> +
>> +dev_size=$((80 * 1024 * 1024))
>> +_scratch_mkfs_sized $dev_size >>$seqres.full 2>&1 || _fail "mkfs failed"
>> +
>> +_scratch_mount
>> +file_blksz="$(_get_file_block_size ${SCRATCH_MNT})"
>> +
>> +# Reserve 1M space
>> +$XFS_IO_PROG -f -c "falloc 0 1M" "${SCRATCH_MNT}/tmp" >> $seqres.full
>> +
>> +# Create a file with logical block numbers close to 0xffffffff
>> +$XFS_IO_PROG -f -c "falloc 0 10M" "${SCRATCH_MNT}/file" >> $seqres.full
>> +max_pos=$(( 0xffffffff * file_blksz ))
>> +finsert_len=$(( max_pos - ((10 + 2) << 20) ))
>> +$XFS_IO_PROG -f -c "finsert 1M ${finsert_len}" "${SCRATCH_MNT}/file" >> $seqres.full
>> +
>> +# Filling up the free space ensures that the pre-allocated space is the reserved space.
>> +nr_free=$(stat -f -c '%f' ${SCRATCH_MNT})
>> +_fill_fs $((nr_free * file_blksz)) ${SCRATCH_MNT}/fill $file_blksz 0 >> $seqres.full 2>&1
>> +sync
>> +
>> +# Remove reserved space to gain free space for allocation
>> +rm -f ${SCRATCH_MNT}/tmp
>> +
>> +# Trying to allocate two blocks triggers BUG_ON.
>> +$XFS_IO_PROG -c "open -ad ${SCRATCH_MNT}/file" -c "pwrite -S 0xff 0 $((2 * file_blksz))" >> $seqres.full
>> +
>> +echo "Silence is golden"
>> +
>> +# success, all done
>> +status=0
>> +exit
>> diff --git a/tests/generic/737.out b/tests/generic/737.out
>> new file mode 100644
>> index 00000000..67b83d78
>> --- /dev/null
>> +++ b/tests/generic/737.out
>> @@ -0,0 +1,2 @@
>> +QA output created by 737
>> +Silence is golden
>> -- 
>> 2.31.1
>>