[PATCH] scsi: mvumi: Replace 1-element arrays with flexible array members

From: Kees Cook
Date: Wed Jan 04 2023 - 20:12:48 EST


One-element arrays (and multi-element arrays being treated as
dynamically sized) are deprecated[1] and are being replaced with
flexible array members in support of the ongoing efforts to tighten the
FORTIFY_SOURCE routines on memcpy(), correctly instrument array indexing
with UBSAN_BOUNDS, and to globally enable -fstrict-flex-arrays=3.

Replace one-element arrays with flexible-array member in struct
mvumi_msg_frame, struct mvumi_rsp_frame, and struct mvumi_hs_header,
adjusting the explicit sizing calculations at the same time.

This results in no functional differences in binary output. An explicit
add is now folded into the size calculation:

│ mov 0x1070(%r14),%eax
│ - add $0x4,%eax
│ - movabs $0xfffffffdc,%rbx
│ + movabs $0xfffffffe0,%rbx
│ add %rax,%rbx

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays

Cc: "James E.J. Bottomley" <jejb@xxxxxxxxxxxxx>
Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
Cc: "Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx>
Cc: linux-scsi@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
drivers/scsi/mvumi.c | 4 ++--
drivers/scsi/mvumi.h | 6 +++---
2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/mvumi.c b/drivers/scsi/mvumi.c
index b3dcb8918618..60c65586f30e 100644
--- a/drivers/scsi/mvumi.c
+++ b/drivers/scsi/mvumi.c
@@ -1841,7 +1841,7 @@ static enum mvumi_qc_result mvumi_send_command(struct mvumi_hba *mhba,
cmd->frame->request_id = mhba->io_seq++;
cmd->request_id = cmd->frame->request_id;
mhba->tag_cmd[cmd->frame->tag] = cmd;
- frame_len = sizeof(*ib_frame) - 4 +
+ frame_len = sizeof(*ib_frame) +
ib_frame->sg_counts * sizeof(struct mvumi_sgl);
if (mhba->hba_capability & HS_CAPABILITY_SUPPORT_DYN_SRC) {
struct mvumi_dyn_list_entry *dle;
@@ -2387,7 +2387,7 @@ static int mvumi_io_attach(struct mvumi_hba *mhba)
struct Scsi_Host *host = mhba->shost;
struct scsi_device *sdev = NULL;
int ret;
- unsigned int max_sg = (mhba->ib_max_size + 4 -
+ unsigned int max_sg = (mhba->ib_max_size -
sizeof(struct mvumi_msg_frame)) / sizeof(struct mvumi_sgl);

host->irq = mhba->pdev->irq;
diff --git a/drivers/scsi/mvumi.h b/drivers/scsi/mvumi.h
index a88c58787b68..1306a4abf19a 100644
--- a/drivers/scsi/mvumi.h
+++ b/drivers/scsi/mvumi.h
@@ -279,7 +279,7 @@ struct mvumi_msg_frame {
u16 request_id;
u16 reserved1;
u8 cdb[MAX_COMMAND_SIZE];
- u32 payload[1];
+ u32 payload[];
};

/*
@@ -294,7 +294,7 @@ struct mvumi_rsp_frame {
u8 req_status;
u8 rsp_flag; /* Indicates the type of Data_Payload.*/
u16 request_id;
- u32 payload[1];
+ u32 payload[];
};

struct mvumi_ob_data {
@@ -380,7 +380,7 @@ struct mvumi_hs_header {
u8 page_code;
u8 checksum;
u16 frame_length;
- u32 frame_content[1];
+ u32 frame_content[];
};

/*
--
2.34.1