linux-hardening - [PATCH] pcmcia: ray_cs: Split memcpy() to avoid bounds check warning

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Date:   Fri,  6 Aug 2021 14:57:33 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Kalle Valo <kvalo@...eaurora.org>
Cc:     Kees Cook <keescook@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] pcmcia: ray_cs: Split memcpy() to avoid bounds check warning

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), memmove(), and memset(), avoid
intentionally writing across neighboring fields.

Split memcpy() for each address range to help memcpy() correctly reason
about the bounds checking. Avoids the future warning:

In function 'fortify_memcpy_chk',
    inlined from 'memcpy_toio' at ./include/asm-generic/io.h:1204:2,
    inlined from 'ray_build_header.constprop' at drivers/net/wireless/ray_cs.c:984:3:
./include/linux/fortify-string.h:285:4: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
  285 |    __write_overflow_field(p_size_field, size);
      |    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Cc: Kalle Valo <kvalo@...eaurora.org>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: linux-wireless@...r.kernel.org
Cc: netdev@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/net/wireless/ray_cs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ray_cs.c b/drivers/net/wireless/ray_cs.c
index 590bd974d94f..d57bbe551630 100644
--- a/drivers/net/wireless/ray_cs.c
+++ b/drivers/net/wireless/ray_cs.c
@@ -982,7 +982,9 @@ AP to AP	1	1	dest AP		src AP		dest	source
 	if (local->net_type == ADHOC) {
 		writeb(0, &ptx->mac.frame_ctl_2);
 		memcpy_toio(ptx->mac.addr_1, ((struct ethhdr *)data)->h_dest,
-			    2 * ADDRLEN);
+			    ADDRLEN);
+		memcpy_toio(ptx->mac.addr_2, ((struct ethhdr *)data)->h_source,
+			    ADDRLEN);
 		memcpy_toio(ptx->mac.addr_3, local->bss_id, ADDRLEN);
 	} else { /* infrastructure */
 
-- 
2.30.2