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Subject[PATCH 6/6][next] ath6kl: wmi: Replace one-element array with flexible-array member in struct wmi_aplist_event
Replace one-element array with flexible-array member in struct
wmi_aplist_event.

It's also worth noting that due to the flexible array transformation,
the size of struct wmi_aplist_event changed (now the size is 8-byte
smaller), and in order to preserve the logic of before the transformation,
the following change is needed:

- if (len < sizeof(struct wmi_aplist_event))
+ if (len <= sizeof(struct wmi_aplist_event))

sizeof(struct wmi_aplist_event) before the flex-array transformation:

struct wmi_aplist_event {
u8 ap_list_ver; /* 0 1 */
u8 num_ap; /* 1 1 */
union wmi_ap_info ap_list[1]; /* 2 8 */

/* size: 10, cachelines: 1, members: 3 */
/* last cacheline: 10 bytes */
};

sizeof(struct wmi_aplist_event) after the flex-array transformation:

struct wmi_aplist_event {
u8 ap_list_ver; /* 0 1 */
u8 num_ap; /* 1 1 */
union wmi_ap_info ap_list[]; /* 2 0 */

/* size: 2, cachelines: 1, members: 3 */
/* last cacheline: 2 bytes */
};

Also, make use of the struct_size() helper and remove unneeded variable
ap_info_entry_size.

This issue was found with the help of Coccinelle and audited and fixed,
manually.

Link: https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays
Link: https://github.com/KSPP/linux/issues/79
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Hi!

It'd be great if someone can confirm or comment on the following
changes described in the changelog text:

- if (len < sizeof(struct wmi_aplist_event))
+ if (len <= sizeof(struct wmi_aplist_event))

Thanks

drivers/net/wireless/ath/ath6kl/wmi.c | 7 ++-----
drivers/net/wireless/ath/ath6kl/wmi.h | 2 +-
2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/ath/ath6kl/wmi.c b/drivers/net/wireless/ath/ath6kl/wmi.c
index 645fb6cae3be..484d37e66ce6 100644
--- a/drivers/net/wireless/ath/ath6kl/wmi.c
+++ b/drivers/net/wireless/ath/ath6kl/wmi.c
@@ -1750,23 +1750,20 @@ static int ath6kl_wmi_snr_threshold_event_rx(struct wmi *wmi, u8 *datap,

static int ath6kl_wmi_aplist_event_rx(struct wmi *wmi, u8 *datap, int len)
{
- u16 ap_info_entry_size;
struct wmi_aplist_event *ev = (struct wmi_aplist_event *) datap;
struct wmi_ap_info_v1 *ap_info_v1;
u8 index;

- if (len < sizeof(struct wmi_aplist_event) ||
+ if (len <= sizeof(struct wmi_aplist_event) ||
ev->ap_list_ver != APLIST_VER1)
return -EINVAL;

- ap_info_entry_size = sizeof(struct wmi_ap_info_v1);
ap_info_v1 = (struct wmi_ap_info_v1 *) ev->ap_list;

ath6kl_dbg(ATH6KL_DBG_WMI,
"number of APs in aplist event: %d\n", ev->num_ap);

- if (len < (int) (sizeof(struct wmi_aplist_event) +
- (ev->num_ap - 1) * ap_info_entry_size))
+ if (len < struct_size(ev, ap_list, ev->num_ap))
return -EINVAL;

/* AP list version 1 contents */
diff --git a/drivers/net/wireless/ath/ath6kl/wmi.h b/drivers/net/wireless/ath/ath6kl/wmi.h
index 6a7fc07cd9aa..a9732660192a 100644
--- a/drivers/net/wireless/ath/ath6kl/wmi.h
+++ b/drivers/net/wireless/ath/ath6kl/wmi.h
@@ -1957,7 +1957,7 @@ union wmi_ap_info {
struct wmi_aplist_event {
u8 ap_list_ver;
u8 num_ap;
- union wmi_ap_info ap_list[1];
+ union wmi_ap_info ap_list[];
} __packed;

/* Developer Commands */
--
2.27.0
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