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Message-Id: <20220924040835.3364912-1-keescook@chromium.org> Date: Fri, 23 Sep 2022 21:08:35 -0700 From: Kees Cook <keescook@...omium.org> To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> Cc: Kees Cook <keescook@...omium.org>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, "Gustavo A. R. Silva" <gustavoars@...nel.org>, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: [PATCH] NFC: hci: Split memcpy() of struct hcp_message flexible array To work around a misbehavior of the compiler's ability to see into composite flexible array structs (as detailed in the coming memcpy() hardening series[1]), split the memcpy() of the header and the payload so no false positive run-time overflow warning will be generated. This split already existed for the "firstfrag" case, so just generalize the logic further. [1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org/ Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> Cc: "David S. Miller" <davem@...emloft.net> Cc: Eric Dumazet <edumazet@...gle.com> Cc: Jakub Kicinski <kuba@...nel.org> Cc: Paolo Abeni <pabeni@...hat.com> Cc: netdev@...r.kernel.org Reported-by: "Gustavo A. R. Silva" <gustavoars@...nel.org> Signed-off-by: Kees Cook <keescook@...omium.org> --- net/nfc/hci/hcp.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/net/nfc/hci/hcp.c b/net/nfc/hci/hcp.c index 05c60988f59a..4902f5064098 100644 --- a/net/nfc/hci/hcp.c +++ b/net/nfc/hci/hcp.c @@ -73,14 +73,12 @@ int nfc_hci_hcp_message_tx(struct nfc_hci_dev *hdev, u8 pipe, if (firstfrag) { firstfrag = false; packet->message.header = HCP_HEADER(type, instruction); - if (ptr) { - memcpy(packet->message.data, ptr, - data_link_len - 1); - ptr += data_link_len - 1; - } } else { - memcpy(&packet->message, ptr, data_link_len); - ptr += data_link_len; + packet->message.header = *ptr++; + } + if (ptr) { + memcpy(packet->message.data, ptr, data_link_len - 1); + ptr += data_link_len - 1; } /* This is the last fragment, set the cb bit */ -- 2.34.1
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