Re: [PATCH net v1] net: dcb: choose correct policy to parse DCB_ATTR_BCN

From: Simon Horman
Date: Mon Jul 31 2023 - 06:03:29 EST


On Mon, Jul 31, 2023 at 12:52:16PM +0800, Lin Ma wrote:
> The dcbnl_bcn_setcfg uses erroneous policy to parse tb[DCB_ATTR_BCN],
> which is introduced in commit 859ee3c43812 ("DCB: Add support for DCB
> BCN"). Please see the comment in below code
>
> static int dcbnl_bcn_setcfg(...)
> {
> ...
> ret = nla_parse_nested_deprecated(..., dcbnl_pfc_up_nest, .. )
> // !!! dcbnl_pfc_up_nest for attributes
> // DCB_PFC_UP_ATTR_0 to DCB_PFC_UP_ATTR_ALL in enum dcbnl_pfc_up_attrs
> ...
> for (i = DCB_BCN_ATTR_RP_0; i <= DCB_BCN_ATTR_RP_7; i++) {
> // !!! DCB_BCN_ATTR_RP_0 to DCB_BCN_ATTR_RP_7 in enum dcbnl_bcn_attrs
> ...
> value_byte = nla_get_u8(data[i]);
> ...
> }
> ...
> for (i = DCB_BCN_ATTR_BCNA_0; i <= DCB_BCN_ATTR_RI; i++) {
> // !!! DCB_BCN_ATTR_BCNA_0 to DCB_BCN_ATTR_RI in enum dcbnl_bcn_attrs
> ...
> value_int = nla_get_u32(data[i]);
> ...
> }
> ...
> }
>
> That is, the nla_parse_nested_deprecated uses dcbnl_pfc_up_nest
> attributes to parse nlattr defined in dcbnl_pfc_up_attrs. But the
> following access code fetch each nlattr as dcbnl_bcn_attrs attributes.
> By looking up the associated nla_policy for dcbnl_bcn_attrs. We can find
> the beginning part of these two policies are "same".
>
> static const struct nla_policy dcbnl_pfc_up_nest[...] = {
> [DCB_PFC_UP_ATTR_0] = {.type = NLA_U8},
> [DCB_PFC_UP_ATTR_1] = {.type = NLA_U8},
> [DCB_PFC_UP_ATTR_2] = {.type = NLA_U8},
> [DCB_PFC_UP_ATTR_3] = {.type = NLA_U8},
> [DCB_PFC_UP_ATTR_4] = {.type = NLA_U8},
> [DCB_PFC_UP_ATTR_5] = {.type = NLA_U8},
> [DCB_PFC_UP_ATTR_6] = {.type = NLA_U8},
> [DCB_PFC_UP_ATTR_7] = {.type = NLA_U8},
> [DCB_PFC_UP_ATTR_ALL] = {.type = NLA_FLAG},
> };
>
> static const struct nla_policy dcbnl_bcn_nest[...] = {
> [DCB_BCN_ATTR_RP_0] = {.type = NLA_U8},
> [DCB_BCN_ATTR_RP_1] = {.type = NLA_U8},
> [DCB_BCN_ATTR_RP_2] = {.type = NLA_U8},
> [DCB_BCN_ATTR_RP_3] = {.type = NLA_U8},
> [DCB_BCN_ATTR_RP_4] = {.type = NLA_U8},
> [DCB_BCN_ATTR_RP_5] = {.type = NLA_U8},
> [DCB_BCN_ATTR_RP_6] = {.type = NLA_U8},
> [DCB_BCN_ATTR_RP_7] = {.type = NLA_U8},
> [DCB_BCN_ATTR_RP_ALL] = {.type = NLA_FLAG},
> // from here is somewhat different
> [DCB_BCN_ATTR_BCNA_0] = {.type = NLA_U32},
> ...
> [DCB_BCN_ATTR_ALL] = {.type = NLA_FLAG},
> };
>
> Therefore, the current code is buggy and this
> nla_parse_nested_deprecated could overflow the dcbnl_pfc_up_nest and use
> the adjacent nla_policy to parse attributes from DCB_BCN_ATTR_BCNA_0.
>
> This patch use correct dcbnl_bcn_nest policy to parse the
> tb[DCB_ATTR_BCN] nested TLV.
>
> Fixes: 859ee3c43812 ("DCB: Add support for DCB BCN")
> Signed-off-by: Lin Ma <linma@xxxxxxxxxx>

Reviewed-by: Simon Horman <horms@xxxxxxxxxx>