linux-hardening - [PATCH] esas2r: Use flex array destination for memcpy()

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Message-Id: <20220901205729.2260982-1-keescook@chromium.org>
Date:   Thu,  1 Sep 2022 13:57:29 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Bradley Grove <linuxdrivers@...otech.com>
Cc:     Kees Cook <keescook@...omium.org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH] esas2r: Use flex array destination for memcpy()

In preparation for FORTIFY_SOURCE performing run-time destination buffer
bounds checking for memcpy(), specify the destination output buffer
explicitly, instead of asking memcpy() to write past the end of what
looked like a fixed-size object. Silences future run-time warning:

  memcpy: detected field-spanning write (size 80) of single field "trc + 1" (size 64)

There is no binary code output differences from this change.

Cc: Bradley Grove <linuxdrivers@...otech.com>
Cc: "James E.J. Bottomley" <jejb@...ux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@...cle.com>
Cc: linux-scsi@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/scsi/esas2r/atioctl.h      | 1 +
 drivers/scsi/esas2r/esas2r_ioctl.c | 3 +--
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/esas2r/atioctl.h b/drivers/scsi/esas2r/atioctl.h
index ff2ad9b38575..dd3437412ffc 100644
--- a/drivers/scsi/esas2r/atioctl.h
+++ b/drivers/scsi/esas2r/atioctl.h
@@ -831,6 +831,7 @@ struct __packed atto_hba_trace {
 	u32 total_length;
 	u32 trace_mask;
 	u8 reserved2[48];
+	u8 contents[];
 };
 
 #define ATTO_FUNC_SCSI_PASS_THRU     0x04
diff --git a/drivers/scsi/esas2r/esas2r_ioctl.c b/drivers/scsi/esas2r/esas2r_ioctl.c
index 08f4e43c7d9e..e003d923acbf 100644
--- a/drivers/scsi/esas2r/esas2r_ioctl.c
+++ b/drivers/scsi/esas2r/esas2r_ioctl.c
@@ -947,10 +947,9 @@ static int hba_ioctl_callback(struct esas2r_adapter *a,
 					break;
 				}
 
-				memcpy(trc + 1,
+				memcpy(trc->contents,
 				       a->fw_coredump_buff + offset,
 				       len);
-
 				hi->data_length = len;
 			} else if (trc->trace_func == ATTO_TRC_TF_RESET) {
 				memset(a->fw_coredump_buff, 0,
-- 
2.34.1