[PATCH net-next 1/2] ath10k: fix gcc-10 zero-length-bounds warnings

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];
      |                             ^~~~~~~

Make records[] a flexible array member to allow this, moving it behind
the other zero-length member that is not accessed in a way that gcc
warns about.

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 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath10k/htt.h b/drivers/net/wireless/ath/ath10k/htt.h
index 8f3710cf28f4..aa056a186402 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[0]; /* ath10k_htt_get_tx_fetch_ind_resp_ids() */
+	struct htt_tx_fetch_record records[];
 } __packed;
 
 static inline void *

-- 
2.26.0

gcc-10 correctly points out a bug with a zero-length array in
struct ath10k_pci:

drivers/net/wireless/ath/ath10k/ahb.c: In function 'ath10k_ahb_remove':
drivers/net/wireless/ath/ath10k/ahb.c:30:9: error: array subscript 0 is outside the bounds of an interior zero-length array 'struct ath10k_ahb[0]' [-Werror=zero-length-bounds]
   30 |  return &((struct ath10k_pci *)ar->drv_priv)->ahb[0];
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from drivers/net/wireless/ath/ath10k/ahb.c:13:
drivers/net/wireless/ath/ath10k/pci.h:185:20: note: while referencing 'ahb'
  185 |  struct ath10k_ahb ahb[0];
      |                    ^~~

The last addition to the struct ignored the comments and added
new members behind the array that must remain last.

Change it to a flexible-array member and move it last again to
make it work correctly, prevent the same thing from happening
again (all compilers warn about flexible-array members in the
middle of a struct) and get it to build without warnings.

Fixes: 521fc37be3d8 ("ath10k: Avoid override CE5 configuration for QCA99X0 chipsets")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/net/wireless/ath/ath10k/pci.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/ath/ath10k/pci.h b/drivers/net/wireless/ath/ath10k/pci.h
index e3cbd259a2dc..862d0901c5b8 100644
--- a/drivers/net/wireless/ath/ath10k/pci.h
+++ b/drivers/net/wireless/ath/ath10k/pci.h

@@ -178,15 +178,16 @@ struct ath10k_pci {
 	 */
 	u32 (*targ_cpu_to_ce_addr)(struct ath10k *ar, u32 addr);
 
+	struct ce_attr *attr;
+	struct ce_pipe_config *pipe_config;
+	struct ce_service_to_pipe *serv_to_pipe;
+
 	/* Keep this entry in the last, memory for struct ath10k_ahb is
 	 * allocated (ahb support enabled case) in the continuation of
 	 * this struct.
 	 */
-	struct ath10k_ahb ahb[0];
+	struct ath10k_ahb ahb[];
 
-	struct ce_attr *attr;
-	struct ce_pipe_config *pipe_config;
-	struct ce_service_to_pipe *serv_to_pipe;
 };
 
 static inline struct ath10k_pci *ath10k_pci_priv(struct ath10k *ar)

-- 
2.26.0

Arnd,

On Sat, May 09, 2020 at 02:06:32PM +0200, Arnd Bergmann wrote:

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];
      |                             ^~~~~~~

Make records[] a flexible array member to allow this, moving it behind
the other zero-length member that is not accessed in a way that gcc
warns about.

Fixes: 3ba225b506a2 ("treewide: Replace zero-length array with flexible-array member")

This treewide patch no longer contains changes for ath10k. I removed them
since Monday (05/04/2020). So, this "Fixes" tag does not apply.

Thanks
--
Gustavo

Arnd Bergmann [off-list ref] wrote:

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];
      |                             ^~~~~~~

Make records[] a flexible array member to allow this, moving it behind
the other zero-length member that is not accessed in a way that gcc
warns about.

Fixes: 22e6b3bc5d96 ("ath10k: add new htt definitions")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kalle Valo <redacted>

2 patches applied to ath-next branch of ath.git, thanks.

9f12bebd512c ath10k: fix gcc-10 zero-length-bounds warnings
32221df6765b ath10k: fix ath10k_pci struct layout

-- 
https://patchwork.kernel.org/patch/11538233/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches