| Message ID | 20200224163252.GA28066@embeddedor (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [next] toshiba: Replace zero-length array with flexible-array member | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (65b2623f395a4e25ab3ff4cff1c9c7623619a22d) |
| snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
| snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 32 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch has no Fixes tags |
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> Date: Mon, 24 Feb 2020 10:32:52 -0600 > 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> Applied.
On 2/24/20 8:32 AM, 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: Seems fine. Acked-by: Geoff Levand <geoff@infradead.org>
diff --git a/drivers/net/ethernet/toshiba/ps3_gelic_net.h b/drivers/net/ethernet/toshiba/ps3_gelic_net.h index 805903dbddcc..68f324ed4eaf 100644 --- a/drivers/net/ethernet/toshiba/ps3_gelic_net.h +++ b/drivers/net/ethernet/toshiba/ps3_gelic_net.h @@ -308,7 +308,7 @@ struct gelic_port { struct gelic_card *card; struct net_device *netdev; enum gelic_port_type type; - long priv[0]; /* long for alignment */ + long priv[]; /* long for alignment */ }; static inline struct gelic_card *port_to_card(struct gelic_port *p) diff --git a/drivers/net/ethernet/toshiba/ps3_gelic_wireless.h b/drivers/net/ethernet/toshiba/ps3_gelic_wireless.h index 4041d946b649..1f203d1ae8db 100644 --- a/drivers/net/ethernet/toshiba/ps3_gelic_wireless.h +++ b/drivers/net/ethernet/toshiba/ps3_gelic_wireless.h @@ -158,7 +158,7 @@ struct gelic_eurus_scan_info { __be32 reserved2; __be32 reserved3; __be32 reserved4; - u8 elements[0]; /* ie */ + u8 elements[]; /* ie */ } __packed; /* the hypervisor returns bbs up to 16 */ diff --git a/drivers/net/ethernet/toshiba/spider_net.h b/drivers/net/ethernet/toshiba/spider_net.h index c0c68cbc898c..05b1a0736835 100644 --- a/drivers/net/ethernet/toshiba/spider_net.h +++ b/drivers/net/ethernet/toshiba/spider_net.h @@ -470,7 +470,7 @@ struct spider_net_card { struct spider_net_extra_stats spider_stats; /* Must be last item in struct */ - struct spider_net_descr darray[0]; + struct spider_net_descr darray[]; }; #endif diff --git a/drivers/net/ethernet/toshiba/tc35815.c b/drivers/net/ethernet/toshiba/tc35815.c index 3fd43d30b20d..b50c3ec3495b 100644 --- a/drivers/net/ethernet/toshiba/tc35815.c +++ b/drivers/net/ethernet/toshiba/tc35815.c @@ -367,7 +367,7 @@ struct TxFD { struct RxFD { struct FDesc fd; - struct BDesc bd[0]; /* variable length */ + struct BDesc bd[]; /* variable length */ }; struct FrFD {
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/net/ethernet/toshiba/ps3_gelic_net.h | 2 +- drivers/net/ethernet/toshiba/ps3_gelic_wireless.h | 2 +- drivers/net/ethernet/toshiba/spider_net.h | 2 +- drivers/net/ethernet/toshiba/tc35815.c | 2 +- 4 files changed, 4 insertions(+), 4 deletions(-)