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Message-ID: <20210823172159.GA25800@embeddedor>
Date: Mon, 23 Aug 2021 12:21:59 -0500
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: Kalle Valo <kvalo@...eaurora.org>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
Cc: ath11k@...ts.infradead.org, linux-wireless@...r.kernel.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
linux-hardening@...r.kernel.org
Subject: [PATCH][next] ath11k: Replace one-element array with flexible-array
member
There is a regular need in the kernel to provide a way to declare having a
dynamically sized set of trailing elements in a structure. Kernel code
should always use "flexible array members"[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].
Refactor the code a bit according to the use of a flexible-array member in
struct scan_chan_list_params instead of a one-element array, and use the
struct_size() helper.
Also, save 25 (too many) bytes that were being allocated:
$ pahole -C channel_param drivers/net/wireless/ath/ath11k/reg.o
struct channel_param {
u8 chan_id; /* 0 1 */
u8 pwr; /* 1 1 */
u32 mhz; /* 2 4 */
/* Bitfield combined with next fields */
u32 half_rate:1; /* 4:16 4 */
u32 quarter_rate:1; /* 4:17 4 */
u32 dfs_set:1; /* 4:18 4 */
u32 dfs_set_cfreq2:1; /* 4:19 4 */
u32 is_chan_passive:1; /* 4:20 4 */
u32 allow_ht:1; /* 4:21 4 */
u32 allow_vht:1; /* 4:22 4 */
u32 allow_he:1; /* 4:23 4 */
u32 set_agile:1; /* 4:24 4 */
u32 psc_channel:1; /* 4:25 4 */
/* XXX 6 bits hole, try to pack */
u32 phy_mode; /* 8 4 */
u32 cfreq1; /* 12 4 */
u32 cfreq2; /* 16 4 */
char maxpower; /* 20 1 */
char minpower; /* 21 1 */
char maxregpower; /* 22 1 */
u8 antennamax; /* 23 1 */
u8 reg_class_id; /* 24 1 */
/* size: 25, cachelines: 1, members: 21 */
/* sum members: 23 */
/* sum bitfield members: 10 bits, bit holes: 1, sum bit holes: 6 bits */
/* last cacheline: 25 bytes */
} __attribute__((__packed__));
as previously, sizeof(struct scan_chan_list_params) was 32 bytes:
$ pahole -C scan_chan_list_params drivers/net/wireless/ath/ath11k/reg.o
struct scan_chan_list_params {
u32 pdev_id; /* 0 4 */
u16 nallchans; /* 4 2 */
struct channel_param ch_param[1]; /* 6 25 */
/* size: 32, cachelines: 1, members: 3 */
/* padding: 1 */
/* last cacheline: 32 bytes */
};
and now with the flexible array transformation it is just 8 bytes:
$ pahole -C scan_chan_list_params drivers/net/wireless/ath/ath11k/reg.o
struct scan_chan_list_params {
u32 pdev_id; /* 0 4 */
u16 nallchans; /* 4 2 */
struct channel_param ch_param[]; /* 6 0 */
/* size: 8, cachelines: 1, members: 3 */
/* padding: 2 */
/* last cacheline: 8 bytes */
};
This helps with the ongoing efforts to globally enable -Warray-bounds and
get us closer to being able to tighten the FORTIFY_SOURCE routines on
memcpy().
This issue was found with the help of Coccinelle and audited and fixed,
manually.
[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/109
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
drivers/net/wireless/ath/ath11k/reg.c | 7 ++-----
drivers/net/wireless/ath/ath11k/wmi.c | 2 +-
drivers/net/wireless/ath/ath11k/wmi.h | 2 +-
3 files changed, 4 insertions(+), 7 deletions(-)
diff --git a/drivers/net/wireless/ath/ath11k/reg.c b/drivers/net/wireless/ath/ath11k/reg.c
index e1a1df169034..c83d265185f1 100644
--- a/drivers/net/wireless/ath/ath11k/reg.c
+++ b/drivers/net/wireless/ath/ath11k/reg.c
@@ -97,7 +97,6 @@ int ath11k_reg_update_chan_list(struct ath11k *ar)
struct channel_param *ch;
enum nl80211_band band;
int num_channels = 0;
- int params_len;
int i, ret;
bands = hw->wiphy->bands;
@@ -117,10 +116,8 @@ int ath11k_reg_update_chan_list(struct ath11k *ar)
if (WARN_ON(!num_channels))
return -EINVAL;
- params_len = sizeof(struct scan_chan_list_params) +
- num_channels * sizeof(struct channel_param);
- params = kzalloc(params_len, GFP_KERNEL);
-
+ params = kzalloc(struct_size(params, ch_param, num_channels),
+ GFP_KERNEL);
if (!params)
return -ENOMEM;
diff --git a/drivers/net/wireless/ath/ath11k/wmi.c b/drivers/net/wireless/ath/ath11k/wmi.c
index 6c253eae9d06..0a634ba04509 100644
--- a/drivers/net/wireless/ath/ath11k/wmi.c
+++ b/drivers/net/wireless/ath/ath11k/wmi.c
@@ -2285,7 +2285,7 @@ int ath11k_wmi_send_scan_chan_list_cmd(struct ath11k *ar,
u16 num_send_chans, num_sends = 0, max_chan_limit = 0;
u32 *reg1, *reg2;
- tchan_info = &chan_list->ch_param[0];
+ tchan_info = chan_list->ch_param;
while (chan_list->nallchans) {
len = sizeof(*cmd) + TLV_HDR_SIZE;
max_chan_limit = (wmi->wmi_ab->max_msg_len[ar->pdev_idx] - len) /
diff --git a/drivers/net/wireless/ath/ath11k/wmi.h b/drivers/net/wireless/ath/ath11k/wmi.h
index d35c47e0b19d..d9c83726f65d 100644
--- a/drivers/net/wireless/ath/ath11k/wmi.h
+++ b/drivers/net/wireless/ath/ath11k/wmi.h
@@ -3608,7 +3608,7 @@ struct wmi_stop_scan_cmd {
struct scan_chan_list_params {
u32 pdev_id;
u16 nallchans;
- struct channel_param ch_param[1];
+ struct channel_param ch_param[];
};
struct wmi_scan_chan_list_cmd {
--
2.27.0
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