linux-hardening - [PATCH 2/3] scsi: esas2r: Switch to flexible array member

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Date:   Fri, 28 May 2021 11:13:36 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Martin K . Petersen" <martin.petersen@...cle.com>
Cc:     Kees Cook <keescook@...omium.org>, Hannes Reinecke <hare@...e.de>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Bradley Grove <linuxdrivers@...otech.com>,
        Artur Paszkiewicz <artur.paszkiewicz@...el.com>,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH 2/3] scsi: esas2r: Switch to flexible array member

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), avoid intentionally writing across
neighboring array fields.

Remove old-style 1-byte array in favor of a flexible array[1] to avoid
future false-positive cross-field memcpy() warning in:

esas2r_vda.c:
	memcpy(vi->cmd.gsv.version_info, esas2r_vdaioctl_versions, ...)

The change in struct size doesn't change other structure sizes (it is
already maxed out to 256 bytes, for example here:

        union {
                struct atto_ioctl_vda_scsi_cmd scsi;
                struct atto_ioctl_vda_flash_cmd flash;
                struct atto_ioctl_vda_diag_cmd diag;
                struct atto_ioctl_vda_cli_cmd cli;
                struct atto_ioctl_vda_smp_cmd smp;
                struct atto_ioctl_vda_cfg_cmd cfg;
                struct atto_ioctl_vda_mgt_cmd mgt;
                struct atto_ioctl_vda_gsv_cmd gsv;
                u8 cmd_info[256];
        } cmd;

No sizes are calculated using the enclosing structure, so no other
updates are needed.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/scsi/esas2r/atioctl.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/esas2r/atioctl.h b/drivers/scsi/esas2r/atioctl.h
index 4aca3d52c851..ff2ad9b38575 100644
--- a/drivers/scsi/esas2r/atioctl.h
+++ b/drivers/scsi/esas2r/atioctl.h
@@ -1141,7 +1141,7 @@ struct __packed atto_ioctl_vda_gsv_cmd {
 
 	u8 rsp_len;
 	u8 reserved[7];
-	u8 version_info[1];
+	u8 version_info[];
 	#define ATTO_VDA_VER_UNSUPPORTED 0xFF
 
 };
-- 
2.25.1