| Message ID | 20200225011846.GA2773@embeddedor (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 7b9307134058cefb9c2416266a7ae6fc4af57915 |
| Delegated to: | Kalle Valo |
| Headers | show |
| Series | [next] p54: Replace zero-length array with flexible-array member | expand |
"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> Patch applied to wireless-drivers-next.git, thanks. 7b9307134058 p54: Replace zero-length array with flexible-array member
diff --git a/drivers/net/wireless/intersil/p54/eeprom.h b/drivers/net/wireless/intersil/p54/eeprom.h index b8f46883a292..1d0aaf54389a 100644 --- a/drivers/net/wireless/intersil/p54/eeprom.h +++ b/drivers/net/wireless/intersil/p54/eeprom.h @@ -24,7 +24,7 @@ struct pda_entry { __le16 len; /* includes both code and data */ __le16 code; - u8 data[0]; + u8 data[]; } __packed; struct eeprom_pda_wrap { @@ -32,7 +32,7 @@ struct eeprom_pda_wrap { __le16 pad; __le16 len; __le32 arm_opcode; - u8 data[0]; + u8 data[]; } __packed; struct p54_iq_autocal_entry { @@ -87,7 +87,7 @@ struct pda_pa_curve_data { u8 channels; u8 points_per_channel; u8 padding; - u8 data[0]; + u8 data[]; } __packed; struct pda_rssi_cal_ext_entry { @@ -119,7 +119,7 @@ struct pda_custom_wrapper { __le16 entry_size; __le16 offset; __le16 len; - u8 data[0]; + u8 data[]; } __packed; /* diff --git a/drivers/net/wireless/intersil/p54/lmac.h b/drivers/net/wireless/intersil/p54/lmac.h index e00761536cfc..8adde6ba35ab 100644 --- a/drivers/net/wireless/intersil/p54/lmac.h +++ b/drivers/net/wireless/intersil/p54/lmac.h @@ -81,7 +81,7 @@ struct p54_hdr { __le16 type; /* enum p54_control_frame_types */ u8 rts_tries; u8 tries; - u8 data[0]; + u8 data[]; } __packed; #define GET_REQ_ID(skb) \ @@ -176,7 +176,7 @@ struct p54_rx_data { u8 rssi_raw; __le32 tsf32; __le32 unalloc0; - u8 align[0]; + u8 align[]; } __packed; enum p54_trap_type { @@ -267,7 +267,7 @@ struct p54_tx_data { } __packed normal; } __packed; u8 unalloc2[2]; - u8 align[0]; + u8 align[]; } __packed; /* unit is ms */ diff --git a/drivers/net/wireless/intersil/p54/p54.h b/drivers/net/wireless/intersil/p54/p54.h index 0a9c1a19380f..3356ea708d81 100644 --- a/drivers/net/wireless/intersil/p54/p54.h +++ b/drivers/net/wireless/intersil/p54/p54.h @@ -126,7 +126,7 @@ struct p54_cal_database { size_t entry_size; size_t offset; size_t len; - u8 data[0]; + u8 data[]; }; #define EEPROM_READBACK_LEN 0x3fc
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/wireless/intersil/p54/eeprom.h | 8 ++++---- drivers/net/wireless/intersil/p54/lmac.h | 6 +++--- drivers/net/wireless/intersil/p54/p54.h | 2 +- 3 files changed, 8 insertions(+), 8 deletions(-)