Messages in this thread | | | Date | Tue, 31 May 2022 12:02:53 +0100 | Subject | Re: [PATCH 2/2] firmware: arm_scmi: Fix pointers arithmetic in Base protocol | From | Robin Murphy <> |
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On 2022-05-30 12:52, Cristian Marussi wrote: > Fix a possible undefined behaviour involving pointer arithmetic in Base > protocol scmi_base_implementation_list_get(). > > cppcheck complains with: > > drivers/firmware/arm_scmi/base.c:190:19: warning: 't->rx.buf' is of type 'void *'. When using void pointers in calculations, the behaviour is undefined. [arithOperationsOnVoidPointer] > list = t->rx.buf + sizeof(*num_ret);
Except we use GNU C, where it is well-defined[1]. We use void pointer arithmetic *all over* Linux, so there really isn't any valid argument that it could be problematic. If this was a common SCMI library intended to be portable then the patch would seem more reasonable, but in Linux-specific driver code it's just pointless churn.
Cheers, Robin.
[1] https://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html
> Fixes: b6f20ff8bd94 ("firmware: arm_scmi: add common infrastructure and support for base protocol") > Cc: Sudeep Holla <sudeep.holla@arm.com> > Signed-off-by: Cristian Marussi <cristian.marussi@arm.com> > --- > drivers/firmware/arm_scmi/base.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/firmware/arm_scmi/base.c b/drivers/firmware/arm_scmi/base.c > index 20fba7370f4e..6d6214d9e68c 100644 > --- a/drivers/firmware/arm_scmi/base.c > +++ b/drivers/firmware/arm_scmi/base.c > @@ -187,7 +187,7 @@ scmi_base_implementation_list_get(const struct scmi_protocol_handle *ph, > > num_skip = t->tx.buf; > num_ret = t->rx.buf; > - list = t->rx.buf + sizeof(*num_ret); > + list = ((u8 *)t->rx.buf) + sizeof(*num_ret); > > do { > size_t real_list_sz;
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