[Patch] Segfault on unaligned lseek() on /dev/sdX (was: [ITP] ddrescue 1.3)

[Christian Franke]

Pedro Alves wrote:
> Christopher Faylor escreveu:
>> On Fri, May 18, 2007 at 09:02:15PM +0200, Christian Franke wrote:
>>> Hi,
>>>
>>> Cygwin 1.5.24-2 segfaults on unaligned lseek() on raw block devices 
>>> with sector size >512 bytes.
>>>
>>> Testcases:
>>> $ dd skip=1000 bs=2047 if=/dev/scd0 of=/dev/null
>>>
>>> $ ddrescue -c 1 /dev/scd0 file.iso
>>>
>>>
>>> This is due to a fixed 512 byte buffer in fhandler_dev_floppy::lseek().
>>> It is still present in HEAD revision.
>>>
>>> The attached patch should fix. It should work for any sector size.
>>> (Smoke-)tested with 1.5.24-2 (too busy to test with current CVS, 
>>> sorry).
>>>
>>> 2007-05-18  Christian Franke <franke@computer.org>
>>>
>>>     * fhandler_floppy.cc (fhandler_dev_floppy::lseek): Fixed 
>>> segfault on
>>>     unaligned seek due to fixed size buffer.
>>>
>>
>> It seems like this could be done without the heavyweight use of malloc,
>> like use an automatic array of length 512 + 4 and calculate an aligned
>> address from that.
>>
>
> Or use alloca instead?
>
> -  char buf[512];
> +  char *buf = (char *) alloca (512);
>

Yes, thanks.

Makes the new patch really simple, see attachment.

Christian

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