Re: [PATCH 04/15] ath10k: fix gcc-10 zero-length-bounds warnings

"Gustavo A. R. Silva" [off-list ref] writes:

On 5/4/20 06:54, Kalle Valo wrote:

quoted

"Gustavo A. R. Silva" [off-list ref] writes:

quoted

Hi Arnd,

On 4/30/20 16:30, Arnd Bergmann wrote:

quoted

gcc-10 started warning about out-of-bounds access for zero-length
arrays:

In file included from drivers/net/wireless/ath/ath10k/core.h:18,
                 from drivers/net/wireless/ath/ath10k/htt_rx.c:8:
drivers/net/wireless/ath/ath10k/htt_rx.c: In function 'ath10k_htt_rx_tx_fetch_ind':
drivers/net/wireless/ath/ath10k/htt.h:1683:17: warning: array subscript 65535 is outside the bounds of an interior zero-length array 'struct htt_tx_fetch_record[0]' [-Wzero-length-bounds]
 1683 |  return (void *)&ind->records[le16_to_cpu(ind->num_records)];
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/wireless/ath/ath10k/htt.h:1676:29: note: while referencing 'records'
 1676 |  struct htt_tx_fetch_record records[0];
      |                             ^~~~~~~

The structure was already converted to have a flexible-array member in
the past, but there are two zero-length members in the end and only
one of them can be a flexible-array member.

Swap the two around to avoid the warning, as 'resp_ids' is not accessed
in a way that causes a warning.

Fixes: 3ba225b506a2 ("treewide: Replace zero-length array with flexible-array member")
Fixes: 22e6b3bc5d96 ("ath10k: add new htt definitions")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/net/wireless/ath/ath10k/htt.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath10k/htt.h b/drivers/net/wireless/ath/ath10k/htt.h
index e7096a73c6ca..7621f0a3dc77 100644
--- a/drivers/net/wireless/ath/ath10k/htt.h
+++ b/drivers/net/wireless/ath/ath10k/htt.h

@@ -1673,8 +1673,8 @@ struct htt_tx_fetch_ind {
 	__le32 token;
 	__le16 num_resp_ids;
 	__le16 num_records;
-	struct htt_tx_fetch_record records[0];
-	__le32 resp_ids[]; /* ath10k_htt_get_tx_fetch_ind_resp_ids() */
+	__le32 resp_ids[0]; /* ath10k_htt_get_tx_fetch_ind_resp_ids() */
+	struct htt_tx_fetch_record records[];
 } __packed;
 
 static inline void *

The treewide patch is an experimental change and, as this change only applies
to my -next tree, I will carry this patch in it, so other people don't have
to worry about this at all.

Gustavo, why do you have ath10k patches in your tree? I prefer that
ath10k patches go through my ath.git tree so that they are reviewed and
tested.

I just wanted to test out a mechanical change. I will remove it from my tree
now and will send a patch to you so you can apply it to your ath.git tree.

Great, thanks.

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