| Message ID | 20200504201224.GA32282@embeddedor (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ath11k: Replace zero-length array with flexible-array | 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] > > 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 <gustavo@embeddedor.com> > Signed-off-by: Kalle Valo <kvalo@codeaurora.org> Patch applied to ath-next branch of ath.git, thanks. 14dd3a71ccb7 ath11k: Replace zero-length array with flexible-array
diff --git a/drivers/net/wireless/ath/ath11k/debug.h b/drivers/net/wireless/ath/ath11k/debug.h index 97e7306c506d..c7edf946ff5c 100644 --- a/drivers/net/wireless/ath/ath11k/debug.h +++ b/drivers/net/wireless/ath/ath11k/debug.h @@ -67,7 +67,7 @@ struct debug_htt_stats_req { u8 peer_addr[ETH_ALEN]; struct completion cmpln; u32 buf_len; - u8 buf[0]; + u8 buf[]; }; struct ath_pktlog_hdr { @@ -77,7 +77,7 @@ struct ath_pktlog_hdr { u16 size; u32 timestamp; u32 type_specific_data; - u8 payload[0]; + u8 payload[]; }; #define ATH11K_HTT_STATS_BUF_SIZE (1024 * 512) diff --git a/drivers/net/wireless/ath/ath11k/debug_htt_stats.h b/drivers/net/wireless/ath/ath11k/debug_htt_stats.h index 23a6baa9e95a..682a6ff222bd 100644 --- a/drivers/net/wireless/ath/ath11k/debug_htt_stats.h +++ b/drivers/net/wireless/ath/ath11k/debug_htt_stats.h @@ -239,7 +239,7 @@ struct htt_tx_pdev_stats_tx_ppdu_stats_tlv_v { */ struct htt_tx_pdev_stats_tried_mpdu_cnt_hist_tlv_v { u32 hist_bin_size; - u32 tried_mpdu_cnt_hist[0]; /* HTT_TX_PDEV_TRIED_MPDU_CNT_HIST */ + u32 tried_mpdu_cnt_hist[]; /* HTT_TX_PDEV_TRIED_MPDU_CNT_HIST */ }; /* == SOC ERROR STATS == */ @@ -550,7 +550,7 @@ struct htt_tx_hwq_stats_cmn_tlv { struct htt_tx_hwq_difs_latency_stats_tlv_v { u32 hist_intvl; /* histogram of ppdu post to hwsch - > cmd status received */ - u32 difs_latency_hist[0]; /* HTT_TX_HWQ_MAX_DIFS_LATENCY_BINS */ + u32 difs_latency_hist[]; /* HTT_TX_HWQ_MAX_DIFS_LATENCY_BINS */ }; /* NOTE: Variable length TLV, use length spec to infer array size */ @@ -586,7 +586,7 @@ struct htt_tx_hwq_fes_result_stats_tlv_v { struct htt_tx_hwq_tried_mpdu_cnt_hist_tlv_v { u32 hist_bin_size; /* Histogram of number of mpdus on tried mpdu */ - u32 tried_mpdu_cnt_hist[0]; /* HTT_TX_HWQ_TRIED_MPDU_CNT_HIST */ + u32 tried_mpdu_cnt_hist[]; /* HTT_TX_HWQ_TRIED_MPDU_CNT_HIST */ }; /* NOTE: Variable length TLV, use length spec to infer array size @@ -1584,7 +1584,7 @@ struct htt_pdev_stats_twt_session_tlv { struct htt_pdev_stats_twt_sessions_tlv { u32 pdev_id; u32 num_sessions; - struct htt_pdev_stats_twt_session_tlv twt_session[0]; + struct htt_pdev_stats_twt_session_tlv twt_session[]; }; enum htt_rx_reo_resource_sample_id_enum { diff --git a/drivers/net/wireless/ath/ath11k/hal_desc.h b/drivers/net/wireless/ath/ath11k/hal_desc.h index 5e200380cca4..a1f747c1c44d 100644 --- a/drivers/net/wireless/ath/ath11k/hal_desc.h +++ b/drivers/net/wireless/ath/ath11k/hal_desc.h @@ -477,7 +477,7 @@ enum hal_tlv_tag { struct hal_tlv_hdr { u32 tl; - u8 value[0]; + u8 value[]; } __packed; #define RX_MPDU_DESC_INFO0_MSDU_COUNT GENMASK(7, 0) @@ -1972,7 +1972,7 @@ struct hal_rx_reo_queue { u32 processed_total_bytes; u32 info5; u32 rsvd[3]; - struct hal_rx_reo_queue_ext ext_desc[0]; + struct hal_rx_reo_queue_ext ext_desc[]; } __packed; /* hal_rx_reo_queue diff --git a/drivers/net/wireless/ath/ath11k/hal_rx.h b/drivers/net/wireless/ath/ath11k/hal_rx.h index e863e4abfcc1..c436191ae1e8 100644 --- a/drivers/net/wireless/ath/ath11k/hal_rx.h +++ b/drivers/net/wireless/ath/ath11k/hal_rx.h @@ -23,7 +23,7 @@ struct hal_rx_wbm_rel_info { struct hal_rx_mon_status_tlv_hdr { u32 hdr; - u8 value[0]; + u8 value[]; }; enum hal_rx_su_mu_coding { diff --git a/drivers/net/wireless/ath/ath11k/hw.h b/drivers/net/wireless/ath/ath11k/hw.h index 9973477ae373..cdec95644758 100644 --- a/drivers/net/wireless/ath/ath11k/hw.h +++ b/drivers/net/wireless/ath/ath11k/hw.h @@ -111,7 +111,7 @@ struct ath11k_hw_params { struct ath11k_fw_ie { __le32 id; __le32 len; - u8 data[0]; + u8 data[]; }; enum ath11k_bd_ie_board_type { diff --git a/drivers/net/wireless/ath/ath11k/wmi.h b/drivers/net/wireless/ath/ath11k/wmi.h index 510f9c6bc1d7..717e87db91cb 100644 --- a/drivers/net/wireless/ath/ath11k/wmi.h +++ b/drivers/net/wireless/ath/ath11k/wmi.h @@ -39,7 +39,7 @@ struct wmi_cmd_hdr { struct wmi_tlv { u32 header; - u8 value[0]; + u8 value[]; } __packed; #define WMI_TLV_LEN GENMASK(15, 0)
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 <gustavo@embeddedor.com> --- drivers/net/wireless/ath/ath11k/debug.h | 4 ++-- drivers/net/wireless/ath/ath11k/debug_htt_stats.h | 8 ++++---- drivers/net/wireless/ath/ath11k/hal_desc.h | 4 ++-- drivers/net/wireless/ath/ath11k/hal_rx.h | 2 +- drivers/net/wireless/ath/ath11k/hw.h | 2 +- drivers/net/wireless/ath/ath11k/wmi.h | 2 +- 6 files changed, 11 insertions(+), 11 deletions(-)