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Message-ID: <Yy6HVVMGdSCyEHbZ@work> Date: Fri, 23 Sep 2022 23:28:05 -0500 From: "Gustavo A. R. Silva" <gustavoars@...nel.org> To: Kees Cook <keescook@...omium.org> Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.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, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH] NFC: hci: Split memcpy() of struct hcp_message flexible array On Fri, Sep 23, 2022 at 09:08:35PM -0700, Kees Cook wrote: > 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> Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org> Thanks! -- Gustavo > --- > 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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