ath6kl: Use struct_group() to avoid size-mismatched casting

In builds with -Warray-bounds, casts from smaller objects to larger
objects will produce warnings. These can be overly conservative, but since
-Warray-bounds has been finding legitimate bugs, it is desirable to turn
it on globally. Instead of casting a u32 to a larger object, redefine
the u32 portion of the header to a separate struct that can be used for
both u32 operations and the distinct header fields. Silences this warning:

drivers/net/wireless/ath/ath6kl/htc_mbox.c: In function 'htc_wait_for_ctrl_msg':
drivers/net/wireless/ath/ath6kl/htc_mbox.c:2275:20: error: array subscript 'struct htc_frame_hdr[0]' is partly outside array bounds of 'u32[1]' {aka 'unsigned int[1]'} [-Werror=array-bounds]
 2275 |         if (htc_hdr->eid != ENDPOINT_0)
      |                    ^~
drivers/net/wireless/ath/ath6kl/htc_mbox.c:2264:13: note: while referencing 'look_ahead'
 2264 |         u32 look_ahead;
      |             ^~~~~~~~~~

This change results in no executable instruction differences.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20211207063538.2767954-1-keescook@chromium.org

diff --git a/drivers/net/wireless/ath/ath6kl/htc.h b/drivers/net/wireless/ath/ath6kl/htc.h
index 112d8a9b8d4319d1a8cbc9dd956911a4c09b39f6..d3534a29c4f059a5e9616aeadf86cafc61ab5c6a 100644 (file)
--- a/drivers/net/wireless/ath/ath6kl/htc.h
+++ b/drivers/net/wireless/ath/ath6kl/htc.h
@@ -153,12 +153,19 @@
  * implementations.
  */
 struct htc_frame_hdr {
-       u8 eid;
-       u8 flags;
-
-       /* length of data (including trailer) that follows the header */
-       __le16 payld_len;
-
+       struct_group_tagged(htc_frame_look_ahead, header,
+               union {
+                       struct {
+                               u8 eid;
+                               u8 flags;
+
+                               /* length of data (including trailer) that follows the header */
+                               __le16 payld_len;
+
+                       };
+                       u32 word;
+               };
+       );
        /* end of 4-byte lookahead */
 
        u8 ctrl[2];

diff --git a/drivers/net/wireless/ath/ath6kl/htc_mbox.c b/drivers/net/wireless/ath/ath6kl/htc_mbox.c
index 998947ef63b6e1940f9a567a5d7fcb974ebe2914..e3874421c4c0c1b574748de1126b2c759a78bbb0 100644 (file)
--- a/drivers/net/wireless/ath/ath6kl/htc_mbox.c
+++ b/drivers/net/wireless/ath/ath6kl/htc_mbox.c
@@ -2260,19 +2260,16 @@ int ath6kl_htc_rxmsg_pending_handler(struct htc_target *target,
 static struct htc_packet *htc_wait_for_ctrl_msg(struct htc_target *target)
 {
        struct htc_packet *packet = NULL;
-       struct htc_frame_hdr *htc_hdr;
-       u32 look_ahead;
+       struct htc_frame_look_ahead look_ahead;
 
-       if (ath6kl_hif_poll_mboxmsg_rx(target->dev, &look_ahead,
+       if (ath6kl_hif_poll_mboxmsg_rx(target->dev, &look_ahead.word,
                                       HTC_TARGET_RESPONSE_TIMEOUT))
                return NULL;
 
        ath6kl_dbg(ATH6KL_DBG_HTC,
-                  "htc rx wait ctrl look_ahead 0x%X\n", look_ahead);
-
-       htc_hdr = (struct htc_frame_hdr *)&look_ahead;
+                  "htc rx wait ctrl look_ahead 0x%X\n", look_ahead.word);
 
-       if (htc_hdr->eid != ENDPOINT_0)
+       if (look_ahead.eid != ENDPOINT_0)
                return NULL;
 
        packet = htc_get_control_buf(target, false);
@@ -2281,8 +2278,8 @@ static struct htc_packet *htc_wait_for_ctrl_msg(struct htc_target *target)
                return NULL;
 
        packet->info.rx.rx_flags = 0;
-       packet->info.rx.exp_hdr = look_ahead;
-       packet->act_len = le16_to_cpu(htc_hdr->payld_len) + HTC_HDR_LENGTH;
+       packet->info.rx.exp_hdr = look_ahead.word;
+       packet->act_len = le16_to_cpu(look_ahead.payld_len) + HTC_HDR_LENGTH;
 
        if (packet->act_len > packet->buf_len)
                goto fail_ctrl_rx;