memory corruption/panic solved ("FAILURE - ATAPI_IDENTIFY no interrupt")

Nate Lawson nate at
Sun Aug 1 23:21:31 PDT 2004

Søren Schmidt wrote:
> Nate Lawson wrote:
>> I've tracked down the source of the memory corruption in -current that
>> results when booting with various CD and DVD drives (especially the ones
>> that come with Thinkpads including T23, R32, T41, etc.)  The panic is
>> obvious when running with INVARIANTS ("memory modified after free") but
>> not so obvious in other configurations.  For instance, without
>> INVARIANTS, part of the rt_info structure is corrupted on my wireless
>> card, resulting in a panic during ifconfig on boot.  This is likely the
>> source of other problems, including phk's ACPI panic (again, only
>> triggered when booting with the CD drive in the bay.)
> OK, first thanks for digging into this!

The other major bug I'm hunting is the EISA probe hanging.  I want 5.3 
to be reliable.

>> The root problem is that ata_timeout() fires and calls ata_pio_read()
>> which overwrites 512 bytes random memory.  There are actually two bugs 
>> here that overwrite memory.  The code path is as follows:
>> 1. ata runs an IDENTIFY command on each drive.  It reaches this stack:
>> ata_getparam()
>> ata_identify_devices()
>> ata_boot_attach()
>> 2. ata_getparam() allocates a request and runs it:
>> ata_alloc_request()
>> loop on retries (2 max)
>> fill out an immediate read request for 512 bytes (DEV_BSIZE)
>> *** Bug 1: transfersize is 512 bytes but sizeof(struct ata_request) is 
>> much less (~80 bytes).
>> ata_queue_request() starts the request and arms a timeout
> Its correct to allocate via ata_alloc_request, the data is *not* put 
> into the request, but into another memory area (atadev->param) so this 
> is not a bug.

You're correct.  Sorry for reading this wrong.  I earlier made a note to 
check the size of atadev->param and mistakenly checked 
sizeof(ata_request).  The params are indeed the right size (512 bytes) 
and the size in ata.h is noted in 16 bit half words.  You might want a 
CTASSERT that DEV_BSIZE == sizeof(ata_params).


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