Messages in this thread | | | Date | Fri, 07 Sep 2012 14:01:12 +0200 | From | Paolo Bonzini <> | Subject | Re: [PATCH 3.6 2/2] target: use a bounce buffer in transport_kmap_data_sg for 0 or 1-page sglist |
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Il 07/09/2012 05:35, Nicholas A. Bellinger ha scritto: >> It is not completely correct for virtual backends, for example I think >> it will always return success for 0-block reads or writes, even if the >> start LBA is out of range. This is also something that I saw with >> PSCSI, and is fixed by these patches. > > Good point !
I spent the morning digging further down the rabbithole, and I found the following testcases:
REPORT LUNS: sg_raw -r8 /dev/sdb a0 00 00 00 00 00 00 00 00 08 00 00 should fail with ILLEGAL REQUEST / INVALID FIELD IN CDB sense does not fail
INQUIRY (VPD PAGE != 0, std != 0): sg_raw /dev/sdb 12 00 83 00 00 00 should fail with ILLEGAL REQUEST / INVALID FIELD IN CDB sense does not fail
MODE SENSE off by one (by two for 10-byte CDB): sg_raw -r20 /dev/sdb 5a 00 0a 00 00 00 00 00 14 00 last byte should be 0x1e it is 0x00
READ: Testcase: sg_raw /dev/sdb 28 00 80 00 00 00 00 00 00 00 should fail with ILLEGAL REQUEST / LBA OUT OF RANGE sense does not fail
Plus:
- missing checks on parameter list length for PR OUT with SPEC_I_PT, UNMAP, SET TARGET PORT GROUPS. In some cases these could lead to reading undefined data.
- no checks for OOM in callers of transport_kmem_data_sg.
>> Also, even though it handles zero-size, it doesn't handle a CDB with a >> small but nonzero allocation length. If you have such a CDB, you can >> overflow the sglist. > > Any particular sg_raw example in mind that can trigger this..?
sg_raw (or even SG_IO) doesn't work because misaligned scatterlists are bounce-buffered by the block layer in blk_map_rq_user.
However, given the above bugs it's better to attack the callers of transport_kmem_data_sg one by one. Again, zero-length CDB support comes for free.
> Ok, if this is a genuine issue then please show how to trigger with > sg_raw, and let's plan on merging this as a -rc6 bugfix in order to > spend some more testing w/ scsi-testsuite across different backends over > the next week.
Doesn't seem to be too important, it can be done for 3.7 except perhaps for PSCSI; I'll put the PSCSI patch at the beginning of the series. I can make scsi-testsuite patches for the above issues, but I'll be glad if someone beats me to it.
Paolo
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