[PATCH AUTOSEL 6.1 10/12] enic: Avoid false positive under FORTIFY_SOURCE

[PATCH AUTOSEL 6.1 10/12] enic: Avoid false positive under FORTIFY_SOURCE

[Sasha Levin]

From: Kees Cook <keescook@chromium.org>

[ Upstream commit 40b9385dd8e6a0515e1c9cd06a277483556b7286 ]

FORTIFY_SOURCE has been ignoring 0-sized destinations while the kernel
code base has been converted to flexible arrays. In order to enforce
the 0-sized destinations (e.g. with __counted_by), the remaining 0-sized
destinations need to be handled. Unfortunately, struct vic_provinfo
resists full conversion, as it contains a flexible array of flexible
arrays, which is only possible with the 0-sized fake flexible array.

Use unsafe_memcpy() to avoid future false positives under
CONFIG_FORTIFY_SOURCE.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/cisco/enic/vnic_vic.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cisco/enic/vnic_vic.c b/drivers/net/ethernet/cisco/enic/vnic_vic.c
index 20fcb20b42ede..66b5778353389 100644
--- a/drivers/net/ethernet/cisco/enic/vnic_vic.c
+++ b/drivers/net/ethernet/cisco/enic/vnic_vic.c
@@ -49,7 +49,8 @@ int vic_provinfo_add_tlv(struct vic_provinfo *vp, u16 type, u16 length,
 
 	tlv->type = htons(type);
 	tlv->length = htons(length);
-	memcpy(tlv->value, value, length);
+	unsafe_memcpy(tlv->value, value, length,
+		      /* Flexible array of flexible arrays */);
 
 	vp->num_tlvs = htonl(ntohl(vp->num_tlvs) + 1);
 	vp->length = htonl(ntohl(vp->length) +
-- 
2.43.0

Re: [PATCH AUTOSEL 6.1 10/12] enic: Avoid false positive under FORTIFY_SOURCE

[Pavel Machek]

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Hi!

> From: Kees Cook <keescook@chromium.org>
> 
> [ Upstream commit 40b9385dd8e6a0515e1c9cd06a277483556b7286 ]
> 
> FORTIFY_SOURCE has been ignoring 0-sized destinations while the kernel
> code base has been converted to flexible arrays. In order to enforce
> the 0-sized destinations (e.g. with __counted_by), the remaining 0-sized
> destinations need to be handled. Unfortunately, struct vic_provinfo
> resists full conversion, as it contains a flexible array of flexible
> arrays, which is only possible with the 0-sized fake flexible array.
> 
> Use unsafe_memcpy() to avoid future false positives under
> CONFIG_FORTIFY_SOURCE.

This prepares for future chagnes, but I don't believe we'll port them
to stable.

Best regards,
								Pavel
-- 
People of Russia, stop Putin before his war on Ukraine escalates.

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Re: [PATCH AUTOSEL 6.1 10/12] enic: Avoid false positive under FORTIFY_SOURCE

[Sasha Levin]

On Mon, Mar 11, 2024 at 10:03:35PM +0100, Pavel Machek wrote:
>Hi!
>
>> From: Kees Cook <keescook@chromium.org>
>>
>> [ Upstream commit 40b9385dd8e6a0515e1c9cd06a277483556b7286 ]
>>
>> FORTIFY_SOURCE has been ignoring 0-sized destinations while the kernel
>> code base has been converted to flexible arrays. In order to enforce
>> the 0-sized destinations (e.g. with __counted_by), the remaining 0-sized
>> destinations need to be handled. Unfortunately, struct vic_provinfo
>> resists full conversion, as it contains a flexible array of flexible
>> arrays, which is only possible with the 0-sized fake flexible array.
>>
>> Use unsafe_memcpy() to avoid future false positives under
>> CONFIG_FORTIFY_SOURCE.
>
>This prepares for future chagnes, but I don't believe we'll port them
>to stable.

Dropped, thanks.

-- 
Thanks,
Sasha