Messages in this thread | | | From | Joel Stanley <> | Date | Wed, 18 Jan 2023 02:38:24 +0000 | Subject | Re: [PATCH] net/ncsi: Silence runtime memcpy() false positive warning |
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On Fri, 2 Dec 2022 at 21:24, Kees Cook <keescook@chromium.org> wrote: > > The memcpy() in ncsi_cmd_handler_oem deserializes nca->data into a > flexible array structure that overlapping with non-flex-array members > (mfr_id) intentionally. Since the mem_to_flex() API is not finished, > temporarily silence this warning, since it is a false positive, using > unsafe_memcpy().
Thanks for sending the fix Kees. I got a bit busy towards the end of the year.
I spent some time looking at how the netlink api was used, and tried to convince myself that a user couldn't send an OEM command that triggered the overflow. It all got a bit tangled up so I didn't come to a conclusion.
Cheers,
Joel
> > Reported-by: Joel Stanley <joel@jms.id.au> > Link: https://lore.kernel.org/netdev/CACPK8Xdfi=OJKP0x0D1w87fQeFZ4A2DP2qzGCRcuVbpU-9=4sQ@mail.gmail.com/ > Cc: Samuel Mendoza-Jonas <sam@mendozajonas.com> > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Eric Dumazet <edumazet@google.com> > Cc: Jakub Kicinski <kuba@kernel.org> > Cc: Paolo Abeni <pabeni@redhat.com> > Cc: netdev@vger.kernel.org > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > net/ncsi/ncsi-cmd.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/ncsi/ncsi-cmd.c b/net/ncsi/ncsi-cmd.c > index dda8b76b7798..fd2236ee9a79 100644 > --- a/net/ncsi/ncsi-cmd.c > +++ b/net/ncsi/ncsi-cmd.c > @@ -228,7 +228,8 @@ static int ncsi_cmd_handler_oem(struct sk_buff *skb, > len += max(payload, padding_bytes); > > cmd = skb_put_zero(skb, len); > - memcpy(&cmd->mfr_id, nca->data, nca->payload); > + unsafe_memcpy(&cmd->mfr_id, nca->data, nca->payload, > + /* skb allocated with enough to load the payload */); > ncsi_cmd_build_header(&cmd->cmd.common, nca); > > return 0; > -- > 2.34.1 >
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