netdev - Re: [PATCH net] wifi: ath12k: fix build vs old compiler

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Message-ID: <834dd0b3-6a2c-4af6-9541-27fd4b21d833@paulmck-laptop>
Date: Tue, 16 Jul 2024 08:39:41 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Kees Cook <kees@...nel.org>
Cc: Jeff Johnson <quic_jjohnson@...cinc.com>,
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
	Kees Cook <keescook@...omium.org>, Kalle Valo <kvalo@...nel.org>,
	Jeff Johnson <jjohnson@...nel.org>,
	Baochen Qiang <quic_bqiang@...cinc.com>,
	linux-wireless@...r.kernel.org, ath12k@...ts.infradead.org,
	Jakub Kicinski <kuba@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net] wifi: ath12k: fix build vs old compiler

On Tue, Jul 16, 2024 at 07:36:40AM -0700, Kees Cook wrote:
> 
> 
> On July 16, 2024 7:03:55 AM PDT, Jeff Johnson <quic_jjohnson@...cinc.com> wrote:
> >On 7/16/2024 7:00 AM, Jeff Johnson wrote:
> >> On 7/16/2024 4:06 AM, Paolo Abeni wrote:
> >>> gcc 11.4.1-3 warns about memcpy() with overlapping pointers:
> >>>
> >>> 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);
> >>>       |                         ^~~~~~
> >>>
> >>> The sum of size_t operands can overflow SIZE_MAX, triggering the
> >>> warning.
> >>> Address the issue using the suitable helper.
> >>>
> >>> Fixes: 4a3c212eee0e ("wifi: ath12k: add basic WoW functionalities")
> >>> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> >>> ---
> >>> Only built tested. Sending directly to net to reduce the RTT, but no
> >>> objections to go through the WiFi tree first
> >>> ---
> >>>  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..bead19db2c9a 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 (size_add(eth_pkt_ofs, eth_pat_len) < ETH_ALEN) {
> >>>  			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 (size_add(eth_pkt_ofs, eth_pat_len) < prot_ofs) {
> >>>  			memcpy(pat, eth_pat, eth_pat_len);
> >>>  			memcpy(bytemask, eth_bytemask, eth_pat_len);
> >>>  
> >> 
> >> Duplicate of https://msgid.link/20240704144341.207317-1-kvalo@kernel.org ??
> >
> >Let me add Kees & Paul to see if they prefer your solution
> 
> Heh, yeah, that works too! Avoid the overflow via saturating addition.
> 
> Reviewed-by: Kees Cook<kees@...nel.org>

Tested-by: Paul E. McKenney <paulmck@...nel.org>

I have no preference between the two, but it would be really nice if a
fix were to hit both -next and mainline sooner rather than later.  ;-)

							Thanx, Paul