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 <[email protected]>
---
include/linux/dma/ti-cppi5.h | 4 ++--
include/linux/efi.h | 2 +-
include/linux/mailbox/zynqmp-ipi-message.h | 2 +-
include/linux/platform_data/cros_ec_commands.h | 4 ++--
include/linux/platform_data/cros_ec_proto.h | 2 +-
kernel/params.c | 2 +-
kernel/tracepoint.c | 2 +-
scripts/kallsyms.c | 2 +-
8 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/include/linux/dma/ti-cppi5.h b/include/linux/dma/ti-cppi5.h
index 579356ae447e..78c911269107 100644
--- a/include/linux/dma/ti-cppi5.h
+++ b/include/linux/dma/ti-cppi5.h
@@ -47,7 +47,7 @@ struct cppi5_host_desc_t {
u32 buf_info1;
u32 org_buf_len;
u64 org_buf_ptr;
- u32 epib[0];
+ u32 epib[];
} __packed;
#define CPPI5_DESC_MIN_ALIGN (16U)
@@ -139,7 +139,7 @@ struct cppi5_desc_epib_t {
*/
struct cppi5_monolithic_desc_t {
struct cppi5_desc_hdr_t hdr;
- u32 epib[0];
+ u32 epib[];
};
#define CPPI5_INFO2_MDESC_DATA_OFFSET_SHIFT (18U)
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 251f1f783cdf..a657850899f0 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1234,7 +1234,7 @@ struct linux_efi_memreserve {
struct {
phys_addr_t base;
phys_addr_t size;
- } entry[0];
+ } entry[];
};
#define EFI_MEMRESERVE_SIZE(count) (sizeof(struct linux_efi_memreserve) + \
diff --git a/include/linux/mailbox/zynqmp-ipi-message.h
b/include/linux/mailbox/zynqmp-ipi-message.h
index 9542b41eacfd..35ce84c8ca02 100644
--- a/include/linux/mailbox/zynqmp-ipi-message.h
+++ b/include/linux/mailbox/zynqmp-ipi-message.h
@@ -14,7 +14,7 @@
*/
struct zynqmp_ipi_message {
size_t len;
- u8 data[0];
+ u8 data[];
};
#endif /* _LINUX_ZYNQMP_IPI_MESSAGE_H_ */
diff --git a/include/linux/platform_data/cros_ec_commands.h
b/include/linux/platform_data/cros_ec_commands.h
index 69210881ebac..451885c697cc 100644
--- a/include/linux/platform_data/cros_ec_commands.h
+++ b/include/linux/platform_data/cros_ec_commands.h
@@ -5065,7 +5065,7 @@ struct ec_response_pd_log {
uint8_t type; /* event type : see PD_EVENT_xx below */
uint8_t size_port; /* [7:5] port number [4:0] payload size in bytes */
uint16_t data; /* type-defined data payload */
- uint8_t payload[0]; /* optional additional data payload: 0..16 bytes */
+ uint8_t payload[]; /* optional additional data payload: 0..16 bytes */
} __ec_align4;
/* The timestamp is the microsecond counter shifted to get about a ms. */
@@ -5691,7 +5691,7 @@ struct ec_response_fp_encryption_status {
struct ec_response_tp_frame_info {
uint32_t n_frames;
- uint32_t frame_sizes[0];
+ uint32_t frame_sizes[];
} __ec_align4;
/* Create a snapshot of current frame readings */
diff --git a/include/linux/platform_data/cros_ec_proto.h
b/include/linux/platform_data/cros_ec_proto.h
index 383243326676..7f03e02c48cd 100644
--- a/include/linux/platform_data/cros_ec_proto.h
+++ b/include/linux/platform_data/cros_ec_proto.h
@@ -69,7 +69,7 @@ struct cros_ec_command {
uint32_t outsize;
uint32_t insize;
uint32_t result;
- uint8_t data[0];
+ uint8_t data[];
};
/**
diff --git a/kernel/params.c b/kernel/params.c
index 8e56f8b12d8f..55c07e3b9903 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -529,7 +529,7 @@ struct module_param_attrs
{
unsigned int num;
struct attribute_group grp;
- struct param_attribute attrs[0];
+ struct param_attribute attrs[];
};
#ifdef CONFIG_SYSFS
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 73956eaff8a9..3ee46cda2692 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -50,7 +50,7 @@ static bool ok_to_free_tracepoints;
*/
struct tp_probes {
struct rcu_head rcu;
- struct tracepoint_func probes[0];
+ struct tracepoint_func probes[];
};
static inline void *allocate_probes(int count)
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 3e8dea6e0a95..6dc3078649fa 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -34,7 +34,7 @@ struct sym_entry {
unsigned int len;
unsigned int start_pos;
unsigned int percpu_absolute;
- unsigned char sym[0];
+ unsigned char sym[];
};
struct addr_range {
