| Message ID | 20200226222722.GA18020@embeddedor (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mtd: rawnand: Replace zero-length array with flexible-array member | expand |
On Thu, Feb 27, 2020 at 7:25 AM Gustavo A. R. Silva <gustavo@embeddedor.com> 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 <gustavo@embeddedor.com> > --- > drivers/mtd/nand/raw/denali.h | 2 +- Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com> > 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(-) >
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 <gustavo@embeddedor.com> > Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com> 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 <gustavo@embeddedor.com> >> Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com> > > Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git nand/next, thanks. > Thanks, Miquel. -- Gustavo
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)
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 <gustavo@embeddedor.com> --- 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(-)