Re: [PATCH] block: bugfix for Amiga partition overflow check patch

[Christian Zigotzky <chzigotzky@xenosoft.de>]

On 01 July 2023 at 10:11 am, Michael Schmitz wrote:
> Hi Christian,
>
> Am 01.07.2023 um 18:40 schrieb Christian Zigotzky:
>> On 01 July 2023 at 04:35 am, Michael Schmitz wrote:
>>> Making 'blk' sector_t (i.e. 64 bit if LBD support is active)
>>> fails the 'blk>0' test in the partition block loop if a
>>> value of (signed int) -1 is used to mark the end of the
>>> partition block list.
>>>
>>> This bug was introduced in patch 3 of my prior Amiga partition
>>> support fixes series, and spotted by Christian Zigotzky when
>>> testing the latest block updates.
>>>
>>> Explicitly cast 'blk' to signed int to allow use of -1 to
>>> terminate the partition block linked list.
>>>
>>> Reported-by: Christian Zigotzky <chzigotzky@xenosoft.de>
>>> Fixes: b6f3f28f60 ("Linux 6.4")
>>> Message-ID: 024ce4fa-cc6d-50a2-9aae-3701d0ebf668@xenosoft.de
>>> Cc: <stable@vger.kernel.org> # 6.4
>>> Link:
>>> https://lore.kernel.org/r/024ce4fa-cc6d-50a2-9aae-3701d0ebf668@xenosoft.de 
>>>
>>>
>>> Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
>>> ---
>>>   block/partitions/amiga.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/block/partitions/amiga.c b/block/partitions/amiga.c
>>> index ed222b9c901b..506921095412 100644
>>> --- a/block/partitions/amiga.c
>>> +++ b/block/partitions/amiga.c
>>> @@ -90,7 +90,7 @@ int amiga_partition(struct parsed_partitions *state)
>>>       }
>>>       blk = be32_to_cpu(rdb->rdb_PartitionList);
>>>       put_dev_sector(sect);
>>> -    for (part = 1; blk>0 && part<=16; part++, put_dev_sector(sect)) {
>>> +    for (part = 1; (s32) blk>0 && part<=16; part++,
>>> put_dev_sector(sect)) {
>>>           /* Read in terms partition table understands */
>>>           if (check_mul_overflow(blk, (sector_t) blksize, &blk)) {
>>>               pr_err("Dev %s: overflow calculating partition block
>>> %llu! Skipping partitions %u and beyond\n",
>> Hello Michael,
>>
>> Thanks for your patch.
>>
>> I patched the latest git kernel source code with your patch today but
>> unfortunately the kernel has reported a bad geometry. (EXT4-fs (sda4):
>> bad geometry: block count ...)
>>
>> dmesg | grep -i sda
>>
>> [    4.025449] sd 0:0:0:0: [sda] 3907029168 512-byte logical blocks:
>> (2.00 TB/1.82 TiB)
>> [    4.071978] sd 0:0:0:0: [sda] 4096-byte physical blocks
>> [    4.119333] sd 0:0:0:0: [sda] Write Protect is off
>> [    4.165958] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
>> [    4.212921] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
>> enabled, doesn't support DPO or FUA
>> [    4.259469] sd 0:0:0:0: [sda] Preferred minimum I/O size 4096 bytes
>> [    4.502519]  sda: RDSK (512) sda1 (DOS^G)(res 2 spb 2) sda2
>> (SFS^B)(res 2 spb 1) sda3 (SFS^B)(res 2 spb 2) sda4 ((res 2 spb 1)
>
> Good - all partitions are recognized again as they ought to be.
>
>> [    4.551981] sd 0:0:0:0: [sda] Attached SCSI disk
>> [   82.421727] EXT4-fs (sda4): bad geometry: block count 319655862
>> exceeds size of device (317690430 blocks)
>
> Now that may be a new bug... or just a filesystem created with 
> incorrect assumptions about partition size.
>
> That is the partition that had reported:
>
>> sda: p4 size 18446744071956107760 extends beyond EOD, truncated
>
> with my patches backed out? I wonder what size mkfs used when creating 
> the filesystem?
>
> The calculated size was clearly incorrect, but the truncated size may 
> also be incorrect. The truncated size is likely that of a partition 
> extending to the end of the disk, but your actual p4 size may have 
> been smaller (your parted -l output had 1992GB which is 8 GB shorter 
> than to EOD).
>
> On the face of it, this does not look like a new bug in the RDB 
> partition code, but I'd rather verify that by inspecting the RDB 
> contents and carrying out the calculations by hand.
>
> Can you please send a copy of the RDB (first few kB of the disk, 
> something like dd if=/dev/sda of=rdb-sda.img bs=512 count=16 should 
> do), and the output of cat /proc/partitions when running a kernel from 
> before my RDB patches?
>
>
Copy of the RDB: https://www.xenosoft.de/rdb-sda.img

cat /proc/partitions:

major minor  #blocks  name

    8        0 1953514584 sda
    8        1     119088 sda1
    8        2    2100096 sda2
    8        3  672670920 sda3
    8        4 1278623448 sda4
   11        0    1048575 sr0
    8       32     250880 sdc
    8       33     249856 sdc1
    8       16  234431064 sdb
    8       17  144364512 sdb1
    8       18          1 sdb2
    8       19   18500608 sdb3
    8       20   40717312 sdb4
    8       21   14684160 sdb5
    8       22   16161792 sdb6
    8       48       1440 sdd
    8       49       1439 sdd1

Thanks