| Message ID | 20220530115237.277077-2-cristian.marussi@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] firmware: arm_scmi: Remove unused local variables | expand |
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;
On Tue, May 31, 2022 at 12:02:53PM +0100, Robin Murphy wrote: > 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. > Hi Robin, thanks for the correction, I'll drop this. Thanks, Cristian > 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;
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;
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); 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(-)