ACK: [SRU][R][PATCH 0/1] scsi: megaraid_sas: Limit NVMe request size to the PRP chain frame

[Andrei Gherzan]

On 26/09/07 04:53PM, Alex Shi via kernel-team wrote:
> BugLink: https://bugs.launchpad.net/bugs/2148534
> 
> SRU Justification:
> 
> [Impact]
> 
> NVMe JBOD devices behind MegaRAID controllers can receive block-layer
> requests larger than the driver's fixed PRP chain frame can describe.
> When that happens, megasas_make_prp_nvme() writes beyond cmd->sg_frame,
> which can fault immediately or silently corrupt a neighbouring in-flight
> command's PRP list.
> 
> [Fix]
> 
> Cherry-pick upstream commit:
> af8c27375733 ("scsi: megaraid_sas: Limit NVMe request size to the PRP chain frame")
> 
> The fix caps max_hw_sectors at the transfer size that fits in the
> per-command PRP chain frame instead of trusting only the firmware MDTS.
> 
> [Test Plan]
> 
> Boot a kernel with the patch on a system with an NVMe JBOD drive behind a
> MegaRAID controller and run large sequential write I/O that previously
> triggered the PRP chain-frame overrun. Confirm the I/O completes without
> the megaraid_sas page fault or neighbouring command corruption.
> 
> [Where problems could occur]
> 
> The change reduces the maximum request size advertised for affected NVMe
> devices. Regressions would most likely appear as reduced throughput for
> large sequential I/O on MegaRAID-attached NVMe devices, but the cap is
> derived from the driver's actual PRP-list capacity and prevents memory
> corruption.
> 
> Thomas Lamprecht (1):
>   scsi: megaraid_sas: Limit NVMe request size to the PRP chain frame
> 
>  drivers/scsi/megaraid/megaraid_sas_base.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)

Acked-by: Andrei Gherzan <andrei.gherzan at canonical.com>

-- 
Andrei Gherzan
gpg: rsa4096/D4D94F67AD0E9640
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