Re: [PATCH v2] ata: libata-scsi: limit simulated SCSI command copy to response length

[Damien Le Moal <dlemoal@kernel.org>]

On 7/2/26 11:01, Karuna Ramkumar wrote:
> The function ata_scsi_rbuf_fill() is used to copy the response of
> emulated SCSI commands from ata_scsi_rbuf to the SCSI command's
> scatterlist.
> 
> Currently, sg_copy_from_buffer() is called with the size argument
> set to ATA_SCSI_RBUF_SIZE (2048 bytes). Since ata_scsi_rbuf is
> zeroed out before the simulation actor is invoked, copying the
> full buffer size causes the remainder of the SCSI command's
> transfer buffer (beyond the actual response length 'len') to be
> overwritten with zeroes. This clobbers any pre-existing sentinel
> values or data in the caller's buffer tail, even though the
> correct residual count is reported via scsi_set_resid().
> 
> Fix this by passing the actual response length 'len' as the copy
> size to sg_copy_from_buffer(), ensuring that the tail of the
> caller's buffer remains untouched. Also, add a defensive check
> to ensure that the actor does not return a length exceeding the
> static buffer capacity. If this occurs, trigger a WARN_ON(),
> fail the command with an aborted command error, and return
> immediately without copying any data.
> 
> The fix was tested by invoking an SCSI SG_IO INQUIRY on
> an ATA disk on vanilla build, and build with the fix. Confirmed
> that the input buffer's tail end remains unmodified with the fix.
> 
> Fixes: 5251ae224d8d ("ata: libata-scsi: Return residual for emulated SCSI commands")
> Assisted-by: Antigravity:gemini-3.5-flash
> Signed-off-by: Karuna Ramkumar <rkaruna@google.com>

Applied to for-7.2-fixes. Thanks!

-- 
Damien Le Moal
Western Digital Research