[PATCH] scsi: megaraid_sas: Add flexible array member for SGLs

[PATCH] scsi: megaraid_sas: Add flexible array member for SGLs

[Kees Cook]

struct MPI2_RAID_SCSI_IO_REQUEST ends with a single SGL, but expects to
copy multiple. Add a flexible array member so the compiler can reason
about the size of the memcpy(). This will avoid the run-time false
positive warning:

  memcpy: detected field-spanning write (size 128) of single field "&r1_cmd->io_request->SGL" at drivers/scsi/megaraid/megaraid_sas_fusion.c:3326 (size 16)

This change results in no binary output differences.

Reported-by: Holger Kiehl <Holger.Kiehl@dwd.de>
Link: https://lore.kernel.org/all/88de8faa-56c4-693d-2d3-67152ee72057@diagnostix.dwd.de/
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumit Saxena <sumit.saxena@broadcom.com>
Cc: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: megaraidlinux.pdl@broadcom.com
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
Holger, are you able to test this change? I expect it should do the
trick, but I don't have the hardware.
---
 drivers/scsi/megaraid/megaraid_sas_fusion.c | 2 +-
 drivers/scsi/megaraid/megaraid_sas_fusion.h | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c b/drivers/scsi/megaraid/megaraid_sas_fusion.c
index fe70f8f11435..6597e118c805 100644
--- a/drivers/scsi/megaraid/megaraid_sas_fusion.c
+++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c
@@ -3323,7 +3323,7 @@ static void megasas_prepare_secondRaid1_IO(struct megasas_instance *instance,
 	/* copy the io request frame as well as 8 SGEs data for r1 command*/
 	memcpy(r1_cmd->io_request, cmd->io_request,
 	       (sizeof(struct MPI2_RAID_SCSI_IO_REQUEST)));
-	memcpy(&r1_cmd->io_request->SGL, &cmd->io_request->SGL,
+	memcpy(r1_cmd->io_request->SGLs, cmd->io_request->SGLs,
 	       (fusion->max_sge_in_main_msg * sizeof(union MPI2_SGE_IO_UNION)));
 	/*sense buffer is different for r1 command*/
 	r1_cmd->io_request->SenseBufferLowAddress =
diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.h b/drivers/scsi/megaraid/megaraid_sas_fusion.h
index 49e9a9048ee7..b677d80e5874 100644
--- a/drivers/scsi/megaraid/megaraid_sas_fusion.h
+++ b/drivers/scsi/megaraid/megaraid_sas_fusion.h
@@ -526,7 +526,10 @@ struct MPI2_RAID_SCSI_IO_REQUEST {
 	__le32			Control;                        /* 0x3C */
 	union MPI2_SCSI_IO_CDB_UNION  CDB;			/* 0x40 */
 	union RAID_CONTEXT_UNION RaidContext;  /* 0x60 */
-	union MPI2_SGE_IO_UNION       SGL;			/* 0x80 */
+	union {
+		union MPI2_SGE_IO_UNION       SGL;		/* 0x80 */
+		DECLARE_FLEX_ARRAY(union MPI2_SGE_IO_UNION, SGLs);
+	};
 };
 
 /*
-- 
2.34.1

Re: [PATCH] scsi: megaraid_sas: Add flexible array member for SGLs

[Holger Kiehl]

On Thu, 5 Jan 2023, Kees Cook wrote:

> struct MPI2_RAID_SCSI_IO_REQUEST ends with a single SGL, but expects to
> copy multiple. Add a flexible array member so the compiler can reason
> about the size of the memcpy(). This will avoid the run-time false
> positive warning:
>
>  memcpy: detected field-spanning write (size 128) of single field "&r1_cmd->io_request->SGL" at drivers/scsi/megaraid/megaraid_sas_fusion.c:3326 (size 16)
>
> This change results in no binary output differences.
>
> Reported-by: Holger Kiehl <Holger.Kiehl@dwd.de>
> Link: https://lore.kernel.org/all/88de8faa-56c4-693d-2d3-67152ee72057@diagnostix.dwd.de/
> Cc: Kashyap Desai <kashyap.desai@broadcom.com>
> Cc: Sumit Saxena <sumit.saxena@broadcom.com>
> Cc: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
> Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
> Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
> Cc: megaraidlinux.pdl@broadcom.com
> Cc: linux-scsi@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> Holger, are you able to test this change? I expect it should do the
> trick, but I don't have the hardware.
>
Yes, that does work. I no longer see 'memcpy: detected field-spanning
write (size 128)'. Tested this on 6.1.4-rc1. Did not see any other
regression.

Regards,
Holger

Re: [PATCH] scsi: megaraid_sas: Add flexible array member for SGLs

[Martin K. Petersen]

Kees,

> struct MPI2_RAID_SCSI_IO_REQUEST ends with a single SGL, but expects
> to copy multiple. Add a flexible array member so the compiler can
> reason about the size of the memcpy(). This will avoid the run-time
> false positive warning:

Applied to 6.3/scsi-staging, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: [PATCH] scsi: megaraid_sas: Add flexible array member for SGLs

[Martin K. Petersen]

On Thu, 05 Jan 2023 21:32:00 -0800, Kees Cook wrote:

> struct MPI2_RAID_SCSI_IO_REQUEST ends with a single SGL, but expects to
> copy multiple. Add a flexible array member so the compiler can reason
> about the size of the memcpy(). This will avoid the run-time false
> positive warning:
> 
>   memcpy: detected field-spanning write (size 128) of single field "&r1_cmd->io_request->SGL" at drivers/scsi/megaraid/megaraid_sas_fusion.c:3326 (size 16)
> 
> [...]

Applied to 6.3/scsi-queue, thanks!

[1/1] scsi: megaraid_sas: Add flexible array member for SGLs
      https://git.kernel.org/mkp/scsi/c/a9a3629592ab

-- 
Martin K. Petersen	Oracle Linux Engineering