| Message ID | 20200507151758.GA4962@embeddedor (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | ec431188b4197aaccfbc6e6ece4fb88f79723635 |
| Delegated to: | Kalle Valo |
| Headers | show |
| Series | wcn36xx: Replace zero-length array with flexible-array | expand |
"Gustavo A. R. Silva" <gustavoars@kernel.org> 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] > > 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> > Signed-off-by: Kalle Valo <kvalo@codeaurora.org> Patch applied to ath-next branch of ath.git, thanks. ec431188b419 wcn36xx: Replace zero-length array with flexible-array
diff --git a/drivers/net/wireless/ath/wcn36xx/hal.h b/drivers/net/wireless/ath/wcn36xx/hal.h index 6ba0fd57c951..aab5a58616fc 100644 --- a/drivers/net/wireless/ath/wcn36xx/hal.h +++ b/drivers/net/wireless/ath/wcn36xx/hal.h @@ -2240,7 +2240,7 @@ struct wcn36xx_hal_process_ptt_msg_req_msg { struct wcn36xx_hal_msg_header header; /* Actual FTM Command body */ - u8 ptt_msg[0]; + u8 ptt_msg[]; } __packed; struct wcn36xx_hal_process_ptt_msg_rsp_msg { @@ -2249,7 +2249,7 @@ struct wcn36xx_hal_process_ptt_msg_rsp_msg { /* FTM Command response status */ u32 ptt_msg_resp_status; /* Actual FTM Command body */ - u8 ptt_msg[0]; + u8 ptt_msg[]; } __packed; struct update_edca_params_req_msg { diff --git a/drivers/net/wireless/ath/wcn36xx/testmode.h b/drivers/net/wireless/ath/wcn36xx/testmode.h index 4c6cfdb46580..09d68fab9add 100644 --- a/drivers/net/wireless/ath/wcn36xx/testmode.h +++ b/drivers/net/wireless/ath/wcn36xx/testmode.h @@ -20,7 +20,7 @@ struct ftm_rsp_msg { u16 msg_id; u16 msg_body_length; u32 resp_status; - u8 msg_response[0]; + u8 msg_response[]; } __packed; /* The request buffer of FTM which contains a byte of command and the request */
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> --- drivers/net/wireless/ath/wcn36xx/hal.h | 4 ++-- drivers/net/wireless/ath/wcn36xx/testmode.h | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-)