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Date: Fri, 26 May 2023 21:31:39 -0700
From: Joe Perches <joe@...ches.com>
To: Kees Cook <keescook@...omium.org>,
Andy Whitcroft <apw@...onical.com>
Cc: Dwaipayan Ray <dwaipayanray1@...il.com>,
Lukas Bulwahn <lukas.bulwahn@...il.com>,
"Gustavo A . R . Silva" <gustavoars@...nel.org>,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3] checkpatch: Check for 0-length and 1-element arrays
On Fri, 2023-05-26 at 19:09 -0700, Kees Cook wrote:
> Fake flexible arrays have been deprecated since last millennium. Proper
> C99 flexible arrays must be used throughout the kernel so
> CONFIG_FORTIFY_SOURCE and CONFIG_UBSAN_BOUNDS can provide proper array
> bounds checking.
Hi again.
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -7430,6 +7430,21 @@ sub process {
> }
> }
>
> +# check for array definition/declarations that should use flexible arrays instead
> + if ($sline =~ /^[\+ ]\s*}\s*;\s*$/ &&
> + $prevline =~ /^\+\s*(?:\}|$Type)\s*$Ident\s*\[\s*(0|1)\s*\]\s*;\s*$/) {
Ahh, now I see why you want to use (?:\}|$Type) to find
struct arrays defined as the last object in another struct.
e.g.: (from drivers/infiniband/hw/mlx5/odp.c)
struct prefetch_mr_work {
struct work_struct work;
u32 pf_flags;
u32 num_sge;
struct {
u64 io_virt;
struct mlx5_ib_mr *mr;
size_t length;
} frags[];
};
grepping for some existing variants, perhaps the $sline test should
be extended to something like:
if ($sline =~ /^[\+ ]\s*}\s*(?:__packed|__attribute__\s*$balanced_parens)?\s*;\s*$/ &&
Dunno, the __packed/__attribute__ uses aren't particularly common.
There are ~1000 uses kernel wide with flexible arrays and only
about 100 with 0 or 1 that could be converted.
like from drivers/net/hyperv/hyperv_net.h:
struct nvsp_6_pd_batch_msg {
struct nvsp_message_header hdr;
u16 count;
u16 guest2host:1;
u16 is_recv:1;
u16 reserved:14;
struct nvsp_6_pd_buf pd_buf[0];
} __packed;
My list (probably incomplete), done with a stupid grep:
(and the 0's are more interesting and much less common than the 1's)
$ git grep -A1 -P '\w+\s+\w+[ \t]*\[\s*[01]?\s*\][ \t]*;'| \
grep -B1 "\-}" | \
grep -B1 -P "\-}.*(__attribute__|__packed)" | \
grep -P '\[\s*[01]\s*\]'
drivers/gpu/drm/hyperv/hyperv_drm_proto.c: struct video_output_situation video_output[1];
drivers/gpu/drm/hyperv/hyperv_drm_proto.c: struct rect rect[1];
drivers/hid/intel-ish-hid/ishtp-hid.h: } __packed reports[1];
drivers/net/ethernet/brocade/bna/bfi_enet.h: u8 rsvd1[1];
drivers/net/ethernet/emulex/benet/be_cmds.h: u32 data_buffer[1];
drivers/net/ethernet/emulex/benet/be_cmds.h: u32 data_buffer[1];
drivers/net/hyperv/hyperv_net.h: struct nvsp_1_receive_buffer_section sections[1];
drivers/net/hyperv/hyperv_net.h: struct nvsp_6_pd_buf pd_buf[0];
drivers/net/wireless/ath/ath10k/htc.h: struct ath10k_htc_record trailer[0];
drivers/net/wireless/ath/ath10k/htt.h: u8 prefetch[0]; /* start of frame, for FW classification engine */
drivers/net/wireless/ath/ath10k/htt.h: u8 prefetch[0]; /* start of frame, for FW classification engine */
drivers/net/wireless/ath/ath10k/wmi.h: struct host_memory_chunk items[1];
drivers/net/wireless/ath/ath10k/wmi.h: u8 tlvs[0];
drivers/net/wireless/ath/ath10k/wmi.h: struct wmi_channel channel_list[1];
drivers/net/wireless/ath/ath10k/wmi.h: u8 data[1];
drivers/net/wireless/ath/ath10k/wmi.h: u8 data[1];
drivers/net/wireless/ath/ath10k/wmi.h: struct wmi_channel peer_chan_list[1];
drivers/net/wireless/ath/ath11k/htc.h: struct ath11k_htc_record trailer[0];
drivers/net/wireless/ath/ath6kl/usb.c: __le32 _pad[1];
drivers/net/wireless/ath/ath6kl/wmi.h: u8 reserved[1];
drivers/net/wireless/ath/ath6kl/wmi.h: struct wmi_pmkid pmkid_list[1];
drivers/net/wireless/ath/ath6kl/wmi.h: u8 reserved[1];
drivers/net/wireless/ath/carl9170/fwcmd.h: u32 vals[0];
drivers/net/wireless/ath/carl9170/fwcmd.h: __le32 regs[0];
drivers/net/wireless/ath/wcn36xx/hal.h: u8 rem_ie_id[1];
drivers/net/wireless/ath/wil6210/fw.h: u8 data[0]; /* free-form data [data_size], see above */
drivers/net/wireless/ath/wil6210/fw.h: struct wil_fw_data_dwrite data[0];
drivers/net/wireless/ath/wil6210/wmi.h: u8 payload[0];
drivers/net/wireless/ath/wil6210/wmi.h: u8 reserved[1];
drivers/net/wireless/atmel/at76c50x-usb.h: u8 reserved[1];
drivers/net/wireless/intel/iwlwifi/fw/api/d3.h: u8 wake_packet[1];
drivers/net/wireless/intel/iwlwifi/fw/api/rx.h: __le32 reserved[1];
drivers/net/wireless/intel/iwlwifi/pcie/internal.h: u8 reserved[1];
drivers/net/wireless/intersil/p54/lmac.h: u8 exclude[1];
drivers/net/wireless/marvell/mwifiex/fw.h: struct mwifiex_chan_scan_param_set chan_scan_param[1];
drivers/net/wireless/marvell/mwifiex/fw.h: u8 bitmap[1];
drivers/net/wireless/marvell/mwifiex/fw.h: struct chan_band_param_set chan_band_param[1];
drivers/net/wireless/marvell/mwifiex/fw.h: u8 ssid[1];
drivers/net/wireless/marvell/mwifiex/fw.h: u8 tsf_data[1];
drivers/net/wireless/marvell/mwifiex/fw.h: u8 value[1];
drivers/net/wireless/marvell/mwifiex/fw.h: u8 tlv_buffer[1];
drivers/net/wireless/marvell/mwifiex/fw.h: struct ieee80211_country_ie_triplet triplet[1];
drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.h: u8 rsv[1];
drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.h: u8 rsv[1];
drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.h: u8 pad[1];
drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.h: u8 pad[1];
drivers/net/wireless/mediatek/mt76/mt7996/mcu.h: u8 __rsv2[1];
drivers/net/wireless/mediatek/mt76/mt7996/mcu.h: u8 __rsv2[1];
drivers/net/wireless/quantenna/qtnfmac/qlink.h: u8 rsvd[1];
drivers/net/wireless/quantenna/qtnfmac/qlink.h: u8 rsvd[1];
drivers/net/wireless/quantenna/qtnfmac/qlink.h: u8 rsvd[1];
drivers/net/wireless/quantenna/qtnfmac/qlink.h: u8 rsvd[1];
drivers/net/wireless/realtek/rtw89/coex.c: u8 val[1];
drivers/net/wireless/ti/wl18xx/acx.h: u8 padding[1];
drivers/net/wireless/ti/wl18xx/conf.h: u8 padding[1];
drivers/net/wireless/ti/wlcore/acx.h: u8 pad[1];
drivers/net/wireless/ti/wlcore/acx.h: u8 pad[1];
drivers/net/wireless/ti/wlcore/acx.h: u8 pad[1];
drivers/net/wireless/ti/wlcore/acx.h: u8 padding[1];
drivers/net/wireless/ti/wlcore/cmd.h: u8 padding[1];
drivers/nvmem/u-boot-env.c: uint8_t data[0];
drivers/platform/x86/dell/dcdbas.h: __u8 command_buffer[1];
drivers/scsi/be2iscsi/be_cmds.h: struct mgmt_conn_info conn_list[1];
drivers/scsi/be2iscsi/be_cmds.h: u32 if_hndl_list[1];
drivers/scsi/be2iscsi/be_main.h: u32 dw[1];
drivers/scsi/be2iscsi/be_main.h: u32 dw[1];
drivers/scsi/ipr.h: struct ipr_hostrcb_config_element elem[1];
drivers/scsi/ipr.h: struct ipr_hostrcb64_config_element elem[1];
drivers/scsi/ipr.h: struct ipr_hostrcb_fabric_desc desc[1];
drivers/scsi/ipr.h: struct ipr_hostrcb64_fabric_desc desc[1];
drivers/scsi/ipr.h: struct ipr_sdt_entry entry[1];
drivers/scsi/ipr.h: struct ipr_software_inq_lid_info lid[1];
drivers/scsi/megaraid/megaraid_sas.h: struct MR_PD_ADDRESS addr[1];
drivers/scsi/megaraid/megaraid_sas.h: struct MR_HOST_DEVICE_LIST_ENTRY host_device_list[1];
drivers/video/fbdev/hyperv_fb.c: struct video_output_situation video_output[1];
drivers/video/fbdev/hyperv_fb.c: struct rect rect[1];
fs/adfs/dir_fplus.h: char bigdirname[1];
fs/crypto/fscrypt_private.h: char encrypted_path[1];
fs/isofs/rock.h: __u8 flags[1];
fs/ksmbd/smb2pdu.h: __u8 Chunks[1]; /* array of srv_copychunk */
fs/ksmbd/smb2pdu.h: char name[1];
fs/ksmbd/smb_common.h: unsigned char DialectsArray[1];
fs/ksmbd/smb_common.h: __le16 FileSystemName[1]; /* do not have to save this - get subset? */
fs/ksmbd/smb_common.h: __le16 VolumeLabel[1];
fs/ntfs/dir.h: ntfschar name[0];
fs/ntfs/layout.h:/* 42*/ ntfschar file_name[0]; /* File name in Unicode. */
fs/ntfs/layout.h: le32 sub_authority[1]; /* At least one sub_authority. */
fs/ntfs/layout.h: ntfschar name[0]; /* The name of the volume in Unicode. */
fs/ntfs/layout.h: u8 data[0]; /* The file's data contents. */
fs/ntfs/layout.h: u8 bitmap[0]; /* Array of bits. */
fs/ntfs/layout.h: u8 reparse_data[0]; /* Meaning depends on reparse_tag. */
fs/reiserfs/reiserfs.h: __u16 entry_sizes[1];
include/linux/greybus/greybus_protocols.h: __u8 data[0];
include/linux/greybus/greybus_protocols.h: __u8 data[0];
include/linux/greybus/greybus_protocols.h: __u8 data[0];
include/linux/greybus/greybus_protocols.h: __u8 report[0];
include/linux/greybus/greybus_protocols.h: __u8 data[0]; /* inbound data */
include/linux/greybus/greybus_protocols.h: __u8 data[0];/* inbound data */
include/linux/hid.h: struct hid_class_descriptor desc[1];
include/linux/hyperv.h: struct vmtransfer_page_range ranges[1];
include/linux/hyperv.h: struct gpa_range range[1];
include/linux/hyperv.h: struct gpa_range range[1];
include/linux/hyperv.h: unsigned char data[1];
include/linux/ieee80211.h: u8 virtual_map[1];
include/linux/mtd/cfi.h: struct cfi_intelext_blockinfo BlockTypes[1];
include/linux/mtd/cfi.h: uint32_t ProtField[1]; /* Not host ordered */
include/linux/mtd/cfi.h: uint32_t ConfField[1]; /* Not host ordered */
include/linux/ti_wilink_st.h: u8 data[0];
include/scsi/fc/fc_ms.h: struct fc_fdmi_port_name port[1];
include/uapi/linux/bpf.h: __u64 __opaque[1];
include/uapi/linux/usb/ch9.h: __le16 wData[1]; /* UTF-16LE encoded */
tools/include/uapi/linux/bpf.h: __u64 __opaque[1];
tools/testing/selftests/bpf/progs/btf_dump_test_case_padding.c: char x[0];
tools/testing/selftests/kvm/include/x86_64/processor.h: u8 extended_state_area[0];
> + if ($1 == '0') {
> + if (ERROR("ZERO_LENGTH_ARRAY",
> + "Use C99 flexible arrays instead of zero-length arrays - see https://github.com/KSPP/linux/issues/78\n" . $hereprev) &&
Instead of github links, how about using:
https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays
Why not combine both of these into a single ERROR?
What's the value in separate types?
if (ERROR("FLEXIBLE_ARRAY",
"Use C99 flexible arrays - see: https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays\n" . $hereprev) &&
$fix && $1 == '0') {
etc...
> + $fix) {
> + $fixed[$fixlinenr - 1] =~ s/\[\s*0\s*\]/[]/;
> + }
> + } else {
> + ERROR("ONE_ELEMENT_ARRAY",
> + "Use C99 flexible arrays instead of one-element arrays - see https://github.com/KSPP/linux/issues/79\n" . $hereprev);
> + }
> + }
> +
> # nested likely/unlikely calls
> if ($line =~ /\b(?:(?:un)?likely)\s*\(\s*!?\s*(IS_ERR(?:_OR_NULL|_VALUE)?|WARN)/) {
> WARN("LIKELY_MISUSE",
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