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Date: Thu, 7 May 2020 14:21:47 -0500
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: "James E.J. Bottomley" <jejb@...ux.ibm.com>,
"Martin K. Petersen" <martin.petersen@...cle.com>
Cc: linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] scsi: libsas: Replace zero-length array with flexible-array
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
drivers/scsi/aic94xx/aic94xx_sds.c | 14 +++++++-------
include/scsi/sas.h | 8 ++++----
2 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/drivers/scsi/aic94xx/aic94xx_sds.c b/drivers/scsi/aic94xx/aic94xx_sds.c
index 3ddc8852bc32..105adba559a1 100644
--- a/drivers/scsi/aic94xx/aic94xx_sds.c
+++ b/drivers/scsi/aic94xx/aic94xx_sds.c
@@ -406,7 +406,7 @@ struct asd_manuf_sec {
u8 sas_addr[SAS_ADDR_SIZE];
u8 pcba_sn[ASD_PCBA_SN_SIZE];
/* Here start the other segments */
- u8 linked_list[0];
+ u8 linked_list[];
} __attribute__ ((packed));
struct asd_manuf_phy_desc {
@@ -449,7 +449,7 @@ struct asd_ms_sb_desc {
u8 type;
u8 node_desc_index;
u8 conn_desc_index;
- u8 _recvd[0];
+ u8 _recvd[];
} __attribute__ ((packed));
#if 0
@@ -478,12 +478,12 @@ struct asd_ms_conn_desc {
u8 size_sideband_desc;
u32 _resvd;
u8 name[16];
- struct asd_ms_sb_desc sb_desc[0];
+ struct asd_ms_sb_desc sb_desc[];
} __attribute__ ((packed));
struct asd_nd_phy_desc {
u8 vp_attch_type;
- u8 attch_specific[0];
+ u8 attch_specific[];
} __attribute__ ((packed));
#if 0
@@ -503,7 +503,7 @@ struct asd_ms_node_desc {
u8 size_phy_desc;
u8 _resvd;
u8 name[16];
- struct asd_nd_phy_desc phy_desc[0];
+ struct asd_nd_phy_desc phy_desc[];
} __attribute__ ((packed));
struct asd_ms_conn_map {
@@ -518,7 +518,7 @@ struct asd_ms_conn_map {
u8 usage_model_id;
u32 _resvd;
struct asd_ms_conn_desc conn_desc[0];
- struct asd_ms_node_desc node_desc[0];
+ struct asd_ms_node_desc node_desc[];
} __attribute__ ((packed));
struct asd_ctrla_phy_entry {
@@ -542,7 +542,7 @@ struct asd_ll_el {
u8 id0;
u8 id1;
__le16 next;
- u8 something_here[0];
+ u8 something_here[];
} __attribute__ ((packed));
static int asd_poll_flash(struct asd_ha_struct *asd_ha)
diff --git a/include/scsi/sas.h b/include/scsi/sas.h
index a5d8ae49198c..4726c1bbec65 100644
--- a/include/scsi/sas.h
+++ b/include/scsi/sas.h
@@ -324,7 +324,7 @@ struct ssp_response_iu {
__be32 response_data_len;
u8 resp_data[0];
- u8 sense_data[0];
+ u8 sense_data[];
} __attribute__ ((packed));
struct ssp_command_iu {
@@ -346,7 +346,7 @@ struct ssp_command_iu {
u8 add_cdb_len:6;
u8 cdb[16];
- u8 add_cdb[0];
+ u8 add_cdb[];
} __attribute__ ((packed));
struct xfer_rdy_iu {
@@ -555,7 +555,7 @@ struct ssp_response_iu {
__be32 response_data_len;
u8 resp_data[0];
- u8 sense_data[0];
+ u8 sense_data[];
} __attribute__ ((packed));
struct ssp_command_iu {
@@ -577,7 +577,7 @@ struct ssp_command_iu {
u8 _r_c:2;
u8 cdb[16];
- u8 add_cdb[0];
+ u8 add_cdb[];
} __attribute__ ((packed));
struct xfer_rdy_iu {
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