[PATCH RFC] wifi: ath12k: workaround fortify warnings in ath12k_wow_convert_8023_to_80211()

[Kalle Valo <kvalo@kernel.org>]

From: Kalle Valo <quic_kvalo@quicinc.com>

Johannes reported with GCC 11.4 there's a fortify warning below. The warning is
not seen with GCC 12.1 nor 13.2. Weirdly moving the other operand of sum to the
other side the warning goes away. This is safe to do as the value of the
operand is check earlier. But the code looks worse with this so I'm not sure
what to do.

In file included from ./include/linux/string.h:374,
                 from ./include/linux/bitmap.h:13,
                 from ./include/linux/cpumask.h:13,
                 from ./include/linux/sched.h:16,
                 from ./include/linux/delay.h:23,
                 from drivers/net/wireless/ath/ath12k/wow.c:7:
drivers/net/wireless/ath/ath12k/wow.c: In function ‘ath12k_wow_convert_8023_to_80211.constprop’:
./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ accessing 18446744073709551611 or more bytes at offsets 0 and 0 overlaps 9223372036854775799 bytes at offset -9223372036854775804 [-Werror=restrict]
  114 | #define __underlying_memcpy     __builtin_memcpy
      |                                 ^
./include/linux/fortify-string.h:637:9: note: in expansion of macro ‘__underlying_memcpy’
  637 |         __underlying_##op(p, q, __fortify_size);                              |         ^~~~~~~~~~~~~
./include/linux/fortify-string.h:682:26: note: in expansion of macro ‘__fortify_memcpy_chk’
  682 | #define memcpy(p, q, s)  __fortify_memcpy_chk(p, q, s,                        |                          ^~~~~~~~~~~~~~~~~~~~
drivers/net/wireless/ath/ath12k/wow.c:190:25: note: in expansion of macro ‘memcpy’
  190 |                         memcpy(pat, eth_pat, eth_pat_len);
      |                         ^~~~~~
./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ accessing 18446744073709551605 or more bytes at offsets 0 and 0 overlaps 9223372036854775787 bytes at offset -9223372036854775798 [-Werror=restrict]
  114 | #define __underlying_memcpy     __builtin_memcpy
      |                                 ^
./include/linux/fortify-string.h:637:9: note: in expansion of macro ‘__underlying_memcpy’
  637 |         __underlying_##op(p, q, __fortify_size);                              |         ^~~~~~~~~~~~~
./include/linux/fortify-string.h:682:26: note: in expansion of macro ‘__fortify_memcpy_chk’
  682 | #define memcpy(p, q, s)  __fortify_memcpy_chk(p, q, s,                        |                          ^~~~~~~~~~~~~~~~~~~~
drivers/net/wireless/ath/ath12k/wow.c:232:25: note: in expansion of macro ‘memcpy’
  232 |                         memcpy(pat, eth_pat, eth_pat_len);
      |                         ^~~~~~

Compile tested only.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Fixes: 4a3c212eee0e ("wifi: ath12k: add basic WoW functionalities")
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
---
 drivers/net/wireless/ath/ath12k/wow.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath12k/wow.c b/drivers/net/wireless/ath/ath12k/wow.c
index c5cba825a84a..e9588bb7561c 100644
--- a/drivers/net/wireless/ath/ath12k/wow.c
+++ b/drivers/net/wireless/ath/ath12k/wow.c
@@ -186,7 +186,7 @@ ath12k_wow_convert_8023_to_80211(struct ath12k *ar,
 	if (eth_pkt_ofs < ETH_ALEN) {
 		pkt_ofs = eth_pkt_ofs + a1_ofs;
 
-		if (eth_pkt_ofs + eth_pat_len < ETH_ALEN) {
+		if (eth_pat_len < ETH_ALEN - eth_pkt_ofs) {
 			memcpy(pat, eth_pat, eth_pat_len);
 			memcpy(bytemask, eth_bytemask, eth_pat_len);
 
@@ -228,7 +228,7 @@ ath12k_wow_convert_8023_to_80211(struct ath12k *ar,
 	} else if (eth_pkt_ofs < prot_ofs) {
 		pkt_ofs = eth_pkt_ofs - ETH_ALEN + a3_ofs;
 
-		if (eth_pkt_ofs + eth_pat_len < prot_ofs) {
+		if (eth_pat_len < prot_ofs - eth_pkt_ofs) {
 			memcpy(pat, eth_pat, eth_pat_len);
 			memcpy(bytemask, eth_bytemask, eth_pat_len);
 

base-commit: c1cacb01f35589bd41360cdb7535afc792c08a7c
-- 
2.39.2