Re: [PATCH v3] block: bugfix for Amiga partition overflow check patch

Michael Schmitz
2023-07-04T19:35:43Z

Hi Greg,

On 4/07/23 18:54, Greg KH wrote:
> On Tue, Jul 04, 2023 at 05:49:55PM +1200, 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.
>>
>> Testing by Christian also exposed another aspect of the old
>> bug fixed in commits fc3d092c6b ("block: fix signed int
>> overflow in Amiga partition support") and b6f3f28f60
>> ("block: add overflow checks for Amiga partition support"):
>>
>> Partitions that did overflow the disk size (due to 32 bit int
>> overflow) were not skipped but truncated to the end of the
>> disk. Users who missed the warning message during boot would
>> go on to create a filesystem with a size exceeding the
>> actual partition size. Now that the 32 bit overflow has been
>> corrected, such filesystems may refuse to mount with a
>> 'filesystem exceeds partition size' error. Users should
>> either correct the partition size, or resize the filesystem
>> before attempting to boot a kernel with the RDB fixes in
>> place.
>>
>> Reported-by: Christian Zigotzky <chzigotzky@xenosoft.de>
>> Fixes: b6f3f28f60 ("block: add overflow checks for Amiga partition support")
> That commit is not in:
>
>> Cc: <stable@vger.kernel.org> # 6.4
> 6.4. It's in Linus's tree only right now.
Sigh ... I should have followed that tree also. I had wondered why the
patches hadn't shown up in Geert's tree yet.
>
> But yes, it's tagged for 5.2 and older kernels to be added to the stable
> tree, so why is this one limited only to 6.4 and not also for 5.2 and
> newer?

Brain fade on my part, same day (and situation) as the botched Fixes:
tag, sorry.

I'll correct that, along with Geert's comment regarding the commit
description.

Cheers,

Michael

>
> thanks,
>
> greg k-h