Messages in this thread | | | Date | Thu, 28 Apr 2022 14:45:07 +0100 | From | Cristian Marussi <> | Subject | Re: [PATCH 04/22] firmware: arm_scmi: Validate BASE_DISCOVER_LIST_PROTOCOLS reply |
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On Thu, Apr 28, 2022 at 11:07:29AM +0100, Sudeep Holla wrote: > On Wed, Mar 30, 2022 at 04:05:33PM +0100, Cristian Marussi wrote: > > Do not blindly trust SCMI backend server reply about list of implemented > > protocols, instead validate the reported length of the list of protocols > > against the real payload size of the message reply. > > > > Fixes: b6f20ff8bd9 ("firmware: arm_scmi: add common infrastructure and support for base protocol") > > Signed-off-by: Cristian Marussi <cristian.marussi@arm.com> > > --- > > drivers/firmware/arm_scmi/base.c | 21 +++++++++++++++++++++ > > 1 file changed, 21 insertions(+) > > > > diff --git a/drivers/firmware/arm_scmi/base.c b/drivers/firmware/arm_scmi/base.c > > index f279146f8110..c1165d1282ef 100644 > > --- a/drivers/firmware/arm_scmi/base.c > > +++ b/drivers/firmware/arm_scmi/base.c > > @@ -189,6 +189,9 @@ scmi_base_implementation_list_get(const struct scmi_protocol_handle *ph, > > list = t->rx.buf + sizeof(*num_ret); > > > > do { > > + size_t real_list_sz; > > + u32 calc_list_sz; > > + > > /* Set the number of protocols to be skipped/already read */ > > *num_skip = cpu_to_le32(tot_num_ret); > > > > @@ -202,6 +205,24 @@ scmi_base_implementation_list_get(const struct scmi_protocol_handle *ph, > > break; > > } > > > > + if (t->rx.len < (sizeof(u32) * 2)) { > > + dev_err(dev, "Truncated reply - rx.len:%zd\n", > > + t->rx.len); > > + ret = -EPROTO; > > + break; > > + } > > + > > + real_list_sz = t->rx.len - sizeof(u32); > > + calc_list_sz = ((loop_num_ret / sizeof(u32)) + > > + !!(loop_num_ret % sizeof(u32))) * sizeof(u32); > > Any reason this can't be (loop_num_ret - 1) / sizeof(u32) + 1 ? >
At first sight could be fine with your easier version BUT what if loop_num_ret is returned as zero ?
real_list_sz should be ZERO length and calc_list_sz
im my version:
calc_list_sz = ((0/4) +!!(0%4)) * 4 ===>> 0
while in the simplified one gets calculated wrong:
calc_list_sz = (0-1)/4 + 1 ====> 1
...moreover being both loop_num_ret and calc_list_sz unsigned I am even not so sure about implicit casting messing things up evenm more :D
So I sticked to the more convoluted approach :D
....Have I missed something else ?
Thanks, Cristian
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