On Sun, 2021-01-03 at 19:49 +0100, Arnd Bergmann wrote:
On Sun, Jan 3, 2021 at 6:00 PM James Bottomley jejb@linux.ibm.com wrote:
On Sun, 2021-01-03 at 17:26 +0100, Arnd Bergmann wrote: [...]
@@ -8209,7 +8208,7 @@ megasas_mgmt_fw_ioctl(struct megasas_instance *instance, if (instance->consistent_mask_64bit) put_unaligned_le64(sense_handle, sense_ptr); else
put_unaligned_le32(sense_handle,sense_ptr);
put_unaligned_le64(sense_handle,sense_ptr); }
This hunk can't be right. It effectively means removing the if.
I'm just trying to restore the state before the regression introduced in my 381d34e376e3 ("scsi: megaraid_sas: Check user-provided offsets").
The old code always stored 'sizeof(long)' bytes into sense_ptr, regardless of instance->consistent_mask_64bit, but it would truncate the address to 32 bit if that was cleared. This was clearly bogus and I tried to make it do something more meaningful, only storing 8 bytes into the structure if it was configured for 64-bit DMA, regardless of the capabilities of the kernel.
Heh, well, all this depends on how the firmware interprets the pointer, for which we don't seem to have a manual. Instinct tells me the flag MFI_FRAME_SENSE64 is what does this and that's conditioned on the same if clause 100 lines above this, so the fix your proposing would still seem to be wrong, because I think when that flag is not set, the device expects the sense pointer to be 32 bit.
However, the if is needed because sense_handle is a dma_addr_t which can be either 32 or 64 bit. What about changing the if to
if (sizeof(dma_addr_t) == 8)
instead?
That would not be useful either, the device surely does not care if the kernel supports 64-bit DMA. What we'd really need here is someone with access to the interface specifications to see how many bytes should be stored in the structure. I suspect always storing 64 bits (as my patch does) is correct, and would send a proper patch to remove the if() if Phil confirms that my test patch fixes the regression.
Well, as I said above, I'm speculating the device does what we tell it, and whether to use 32 or 64 bits for the sense pointer definitely seems to be a flag the driver controls ... we really need someone with access to the programming manual to tell us if this speculation is accurate, though.
James