Re: [Qemu-devel] [PATCH 1.1] scsi: Add assertion for use-after-free errors

[Paolo Bonzini]

Il 03/05/2012 22:58, Stefan Weil ha scritto:
> Am 03.05.2012 19:36, schrieb Stefan Weil:
>> The QEMU emulation which is currently used with Raspberry PI images
>> (qemu-system-arm -M versatilepb ...) accesses memory which was freed.
>>
>> Valgrind output (extract):
>>
>> ==17857== Invalid write of size 4
>> ==17857== at 0x24EB06: scsi_req_unref (scsi-bus.c:1273)
>> ==17857== by 0x24FFAE: scsi_read_complete (scsi-disk.c:277)
>> ==17857== by 0x152ACC: bdrv_co_em_bh (block.c:3363)
>> ==17857== by 0x13D49C: qemu_bh_poll (async.c:71)
>> ==17857== by 0x211A8C: main_loop_wait (main-loop.c:503)
>> ==17857== by 0x207954: main_loop (vl.c:1555)
>> ==17857== by 0x20E9C9: main (vl.c:3653)
>> ==17857== Address 0x1c54383c is 12 bytes inside a block of size 260
>> free'd
>> ==17857== at 0x4824B3A: free (vg_replace_malloc.c:366)
>> ==17857== by 0x20ADFA: free_and_trace (vl.c:2250)
>> ==17857== by 0x4899FC5: g_free (in /lib/libglib-2.0.so.0.2400.1)
>> ==17857== by 0x24EB3B: scsi_req_unref (scsi-bus.c:1277)
>> ==17857== by 0x24F003: scsi_req_complete (scsi-bus.c:1383)
>> ==17857== by 0x25022A: scsi_read_data (scsi-disk.c:334)
>> ==17857== by 0x24EB9F: scsi_req_continue (scsi-bus.c:1289)
>> ==17857== by 0x1C7787: lsi_do_dma (lsi53c895a.c:575)
>> ==17857== by 0x1C8CDA: lsi_execute_script (lsi53c895a.c:1147)
>> ==17857== by 0x1C74EA: lsi_resume_script (lsi53c895a.c:510)
>> ==17857== by 0x1C7ECD: lsi_transfer_data (lsi53c895a.c:746)
>> ==17857== by 0x24EC90: scsi_req_data (scsi-bus.c:1307)

Yes, this was reported by David Gibson too.  Interesting that
virtio-scsi doesn't show it, probably it's the sglist support that hides
it.  I queued the fix and I'm sending the pull request in a matter of
minutes.  The patch is a good addition so I queued it too, thanks.

Paolo