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 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]>
---
drivers/mtd/nand/raw/denali.h | 2 +-
drivers/mtd/nand/raw/marvell_nand.c | 2 +-
drivers/mtd/nand/raw/meson_nand.c | 2 +-
drivers/mtd/nand/raw/mtk_nand.c | 2 +-
drivers/mtd/nand/raw/nand_hynix.c | 2 +-
drivers/mtd/nand/raw/sunxi_nand.c | 2 +-
6 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/mtd/nand/raw/denali.h b/drivers/mtd/nand/raw/denali.h
index e5cdcda56d14..ac46eb7956ce 100644
--- a/drivers/mtd/nand/raw/denali.h
+++ b/drivers/mtd/nand/raw/denali.h
@@ -328,7 +328,7 @@ struct denali_chip {
struct nand_chip chip;
struct list_head node;
unsigned int nsels;
- struct denali_chip_sel sels[0];
+ struct denali_chip_sel sels[];
};
/**
diff --git a/drivers/mtd/nand/raw/marvell_nand.c b/drivers/mtd/nand/raw/marvell_nand.c
index fb5abdcfb007..7082bef1c8a7 100644
--- a/drivers/mtd/nand/raw/marvell_nand.c
+++ b/drivers/mtd/nand/raw/marvell_nand.c
@@ -334,7 +334,7 @@ struct marvell_nand_chip {
int addr_cyc;
int selected_die;
unsigned int nsels;
- struct marvell_nand_chip_sel sels[0];
+ struct marvell_nand_chip_sel sels[];
};
static inline struct marvell_nand_chip *to_marvell_nand(struct nand_chip *chip)
diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
index 9f17b5b8efbf..f6fb5c0e6255 100644
--- a/drivers/mtd/nand/raw/meson_nand.c
+++ b/drivers/mtd/nand/raw/meson_nand.c
@@ -118,7 +118,7 @@ struct meson_nfc_nand_chip {
u8 *data_buf;
__le64 *info_buf;
u32 nsels;
- u8 sels[0];
+ u8 sels[];
};
struct meson_nand_ecc {
diff --git a/drivers/mtd/nand/raw/mtk_nand.c b/drivers/mtd/nand/raw/mtk_nand.c
index b8305e39ab51..ef149e8b26d0 100644
--- a/drivers/mtd/nand/raw/mtk_nand.c
+++ b/drivers/mtd/nand/raw/mtk_nand.c
@@ -131,7 +131,7 @@ struct mtk_nfc_nand_chip {
u32 spare_per_sector;
int nsels;
- u8 sels[0];
+ u8 sels[];
/* nothing after this field */
};
diff --git a/drivers/mtd/nand/raw/nand_hynix.c b/drivers/mtd/nand/raw/nand_hynix.c
index 194e4227aefe..7caedaa5b9e5 100644
--- a/drivers/mtd/nand/raw/nand_hynix.c
+++ b/drivers/mtd/nand/raw/nand_hynix.c
@@ -26,7 +26,7 @@
struct hynix_read_retry {
int nregs;
const u8 *regs;
- u8 values[0];
+ u8 values[];
};
/**
diff --git a/drivers/mtd/nand/raw/sunxi_nand.c b/drivers/mtd/nand/raw/sunxi_nand.c
index 37a4ac0dd85b..6ede3934a5f4 100644
--- a/drivers/mtd/nand/raw/sunxi_nand.c
+++ b/drivers/mtd/nand/raw/sunxi_nand.c
@@ -195,7 +195,7 @@ struct sunxi_nand_chip {
u32 timing_cfg;
u32 timing_ctl;
int nsels;
- struct sunxi_nand_chip_sel sels[0];
+ struct sunxi_nand_chip_sel sels[];
};
static inline struct sunxi_nand_chip *to_sunxi_nand(struct nand_chip *nand)
--
2.25.0
On Thu, Feb 27, 2020 at 7:25 AM Gustavo A. R. Silva
<[email protected]> wrote:
>
> 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 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]>
> ---
> drivers/mtd/nand/raw/denali.h | 2 +-
Acked-by: Masahiro Yamada <[email protected]>
> drivers/mtd/nand/raw/marvell_nand.c | 2 +-
> drivers/mtd/nand/raw/meson_nand.c | 2 +-
> drivers/mtd/nand/raw/mtk_nand.c | 2 +-
> drivers/mtd/nand/raw/nand_hynix.c | 2 +-
> drivers/mtd/nand/raw/sunxi_nand.c | 2 +-
> 6 files changed, 6 insertions(+), 6 deletions(-)
>
--
Best Regards
Masahiro Yamada
On Wed, 2020-02-26 at 22:27:22 UTC, "Gustavo A. R. Silva" wrote:
> 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 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]>
> Acked-by: Masahiro Yamada <[email protected]>
Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next, thanks.
Miquel
On 3/10/20 1:31 PM, Miquel Raynal wrote:
>>
>> [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]>
>> Acked-by: Masahiro Yamada <[email protected]>
>
> Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next, thanks.
>
Thanks, Miquel.
--
Gustavo