qlogic: Replace zero-length array with flexible-array member
Subsystems (4)
PATCH 1/1 qlogic: Replace zero-length array with flexible-array member
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]
This issue was detected 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")
--- drivers/net/ethernet/qlogic/netxen/netxen_nic.h | 2 +- drivers/net/ethernet/qlogic/qlcnic/qlcnic.h | 8 ++++---- 2 files changed, 5 insertions(+), 5 deletions(-)
drivers/net/ethernet/qlogic/netxen/netxen_nic.h +1 -1
@@ -1316,7 +1316,7 @@ struct netxen_minidump_template_hdr {u32 driver_info_word4;u32 saved_state_array[NX_DUMP_STATE_ARRAY_LEN ];u32 capture_size_array[NX_DUMP_CAP_SIZE_ARRAY_LEN ]; -u32 rsvd[0 ]; +u32 rsvd[]; };/* Common Entry Header: Common to All Entry Types */
drivers/net/ethernet/qlogic/qlcnic/qlcnic.h +4 -4
@@ -418,7 +418,7 @@ struct qlcnic_83xx_dump_template_hdr {u32 saved_state[16 ];u32 cap_sizes[8 ];u32 ocm_wnd_reg[16 ]; -u32 rsvd[0 ]; +u32 rsvd[]; };struct qlcnic_82xx_dump_template_hdr {
@@ -436,7 +436,7 @@ struct qlcnic_82xx_dump_template_hdr {u32 cap_sizes[8 ];u32 rsvd[7 ];u32 capabilities; -u32 rsvd1[0 ]; +u32 rsvd1[]; };#define QLC_PEX_DMA_READ_SIZE (PAGE_SIZE * 16)
@@ -740,7 +740,7 @@ struct qlcnic_hostrq_rx_ctx {The following is packed: - N hostrq_rds_rings - N hostrq_sds_rings */ -char data[0 ]; +char data[]; } __packed;struct qlcnic_cardrsp_rds_ring {
@@ -769,7 +769,7 @@ struct qlcnic_cardrsp_rx_ctx {The following is packed: - N cardrsp_rds_rings - N cardrs_sds_rings */ -char data[0 ]; +char data[]; } __packed;#define SIZEOF_HOSTRQ_RX (HOSTRQ_RX , rds_rings, sds_rings) \
Signature · 1 line
2.25.0
From: "Gustavo A. R. Silva" <[email protected]>
Date: Mon, 24 Feb 2020 18:03:55 -0600
Quoted 22 lines
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]
Quoted 7 lines
This issue was detected with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit76497732932f("cxgb3/l2t: Fix undefined behaviour")Signed-off-by Gustavo A. R. Silva <[email protected]>
Applied.