* [PATCH] sparc64: Replace zero-length array with flexible-array
@ 2020-05-07 19:23 ` Gustavo A. R. Silva
0 siblings, 0 replies; 6+ messages in thread
From: Gustavo A. R. Silva @ 2020-05-07 19:23 UTC (permalink / raw)
To: David S. Miller; +Cc: sparclinux, linux-kernel
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@kernel.org>
---
arch/sparc/kernel/cpumap.c | 2 +-
arch/sparc/kernel/ds.c | 8 ++++----
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/sparc/kernel/cpumap.c b/arch/sparc/kernel/cpumap.c
index 1cb62bfeaa1f..f07ea88a83af 100644
--- a/arch/sparc/kernel/cpumap.c
+++ b/arch/sparc/kernel/cpumap.c
@@ -50,7 +50,7 @@ struct cpuinfo_tree {
/* Offsets into nodes[] for each level of the tree */
struct cpuinfo_level level[CPUINFO_LVL_MAX];
- struct cpuinfo_node nodes[0];
+ struct cpuinfo_node nodes[];
};
diff --git a/arch/sparc/kernel/ds.c b/arch/sparc/kernel/ds.c
index 75232cbd58bf..522e5b51050c 100644
--- a/arch/sparc/kernel/ds.c
+++ b/arch/sparc/kernel/ds.c
@@ -87,7 +87,7 @@ struct ds_reg_req {
__u64 handle;
__u16 major;
__u16 minor;
- char svc_id[0];
+ char svc_id[];
};
struct ds_reg_ack {
@@ -701,12 +701,12 @@ struct ds_var_hdr {
struct ds_var_set_msg {
struct ds_var_hdr hdr;
- char name_and_value[0];
+ char name_and_value[];
};
struct ds_var_delete_msg {
struct ds_var_hdr hdr;
- char name[0];
+ char name[];
};
struct ds_var_resp {
@@ -989,7 +989,7 @@ struct ds_queue_entry {
struct ds_info *dp;
int req_len;
int __pad;
- u64 req[0];
+ u64 req[];
};
static void process_ds_work(void)
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH] sparc64: Replace zero-length array with flexible-array
@ 2020-05-07 19:23 ` Gustavo A. R. Silva
0 siblings, 0 replies; 6+ messages in thread
From: Gustavo A. R. Silva @ 2020-05-07 19:23 UTC (permalink / raw)
To: David S. Miller; +Cc: sparclinux, linux-kernel
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@kernel.org>
---
arch/sparc/kernel/cpumap.c | 2 +-
arch/sparc/kernel/ds.c | 8 ++++----
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/sparc/kernel/cpumap.c b/arch/sparc/kernel/cpumap.c
index 1cb62bfeaa1f..f07ea88a83af 100644
--- a/arch/sparc/kernel/cpumap.c
+++ b/arch/sparc/kernel/cpumap.c
@@ -50,7 +50,7 @@ struct cpuinfo_tree {
/* Offsets into nodes[] for each level of the tree */
struct cpuinfo_level level[CPUINFO_LVL_MAX];
- struct cpuinfo_node nodes[0];
+ struct cpuinfo_node nodes[];
};
diff --git a/arch/sparc/kernel/ds.c b/arch/sparc/kernel/ds.c
index 75232cbd58bf..522e5b51050c 100644
--- a/arch/sparc/kernel/ds.c
+++ b/arch/sparc/kernel/ds.c
@@ -87,7 +87,7 @@ struct ds_reg_req {
__u64 handle;
__u16 major;
__u16 minor;
- char svc_id[0];
+ char svc_id[];
};
struct ds_reg_ack {
@@ -701,12 +701,12 @@ struct ds_var_hdr {
struct ds_var_set_msg {
struct ds_var_hdr hdr;
- char name_and_value[0];
+ char name_and_value[];
};
struct ds_var_delete_msg {
struct ds_var_hdr hdr;
- char name[0];
+ char name[];
};
struct ds_var_resp {
@@ -989,7 +989,7 @@ struct ds_queue_entry {
struct ds_info *dp;
int req_len;
int __pad;
- u64 req[0];
+ u64 req[];
};
static void process_ds_work(void)
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] sparc64: Replace zero-length array with flexible-array
2020-05-07 19:23 ` Gustavo A. R. Silva
@ 2020-05-08 1:49 ` David Miller
-1 siblings, 0 replies; 6+ messages in thread
From: David Miller @ 2020-05-08 1:49 UTC (permalink / raw)
To: gustavoars; +Cc: sparclinux, linux-kernel
From: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Date: Thu, 7 May 2020 14:23:02 -0500
> 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@kernel.org>
Applied, thank you.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] sparc64: Replace zero-length array with flexible-array
@ 2020-05-08 1:49 ` David Miller
0 siblings, 0 replies; 6+ messages in thread
From: David Miller @ 2020-05-08 1:49 UTC (permalink / raw)
To: gustavoars; +Cc: sparclinux, linux-kernel
From: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Date: Thu, 7 May 2020 14:23:02 -0500
> 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@kernel.org>
Applied, thank you.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] sparc64: Replace zero-length array with flexible-array
2020-05-08 1:49 ` David Miller
@ 2020-05-12 18:05 ` Gustavo A. R. Silva
-1 siblings, 0 replies; 6+ messages in thread
From: Gustavo A. R. Silva @ 2020-05-12 18:05 UTC (permalink / raw)
To: David Miller; +Cc: sparclinux, linux-kernel
On Thu, May 07, 2020 at 06:49:16PM -0700, David Miller wrote:
> From: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Date: Thu, 7 May 2020 14:23:02 -0500
>
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>
> Applied, thank you.
Thanks, Dave.
--
Gustavo
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-05-12 18:05 UTC | newest]
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2020-05-07 19:23 [PATCH] sparc64: Replace zero-length array with flexible-array Gustavo A. R. Silva
2020-05-07 19:23 ` Gustavo A. R. Silva
2020-05-08 1:49 ` David Miller
2020-05-08 1:49 ` David Miller
2020-05-12 18:05 ` Gustavo A. R. Silva
2020-05-12 18:05 ` Gustavo A. R. Silva
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