The current codebase makes use of one-element arrays in the following
form:
struct something {
int length;
u8 data[1];
};
struct something *instance;
instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL);
instance->length = size;
memcpy(instance->data, source, size);
but the preferred mechanism to declare variable-length types such as
these ones is a flexible array member[1][2], introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
This issue was found with the help of Coccinelle and audited _manually_.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
Changes in v2:
- Don't use struct_size() for now.
- Update subject line and changelog text.
drivers/acpi/acpica/utids.c | 2 +-
include/acpi/actypes.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/acpica/utids.c b/drivers/acpi/acpica/utids.c
index 3bb06935a2ad3..225f3c60203c7 100644
--- a/drivers/acpi/acpica/utids.c
+++ b/drivers/acpi/acpica/utids.c
@@ -263,7 +263,7 @@ acpi_ut_execute_CID(struct acpi_namespace_node *device_node,
* 3) Size of the actual CID strings
*/
cid_list_size = sizeof(struct acpi_pnp_device_id_list) +
- ((count - 1) * sizeof(struct acpi_pnp_device_id)) +
+ count * sizeof(struct acpi_pnp_device_id) +
string_area_size;
cid_list = ACPI_ALLOCATE_ZEROED(cid_list_size);
diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h
index 4defed58ea338..c7bcda0ad366a 100644
--- a/include/acpi/actypes.h
+++ b/include/acpi/actypes.h
@@ -1145,7 +1145,7 @@ struct acpi_pnp_device_id {
struct acpi_pnp_device_id_list {
u32 count; /* Number of IDs in Ids array */
u32 list_size; /* Size of list, including ID strings */
- struct acpi_pnp_device_id ids[1]; /* ID array */
+ struct acpi_pnp_device_id ids[]; /* ID array */
};
/*
--
2.27.0
On Tue, Jun 2, 2020 at 11:34 PM Gustavo A. R. Silva
<[email protected]> wrote:
>
> The current codebase makes use of one-element arrays in the following
> form:
>
> struct something {
> int length;
> u8 data[1];
> };
>
> struct something *instance;
>
> instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL);
> instance->length = size;
> memcpy(instance->data, source, size);
>
> but the preferred mechanism to declare variable-length types such as
> these ones is a flexible array member[1][2], introduced in C99:
>
> struct foo {
> int stuff;
> struct boo array[];
> };
>
> By making use of the mechanism above, we will get a compiler warning
> in case the flexible array does not occur last in the structure, which
> will help us prevent some kind of undefined behavior bugs from being
> inadvertently introduced[3] to the codebase from now on.
>
> This issue was found with the help of Coccinelle and audited _manually_.
>
> [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
> [2] https://github.com/KSPP/linux/issues/21
> [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
Erik, can you take this to the upstream, please?
> ---
> Changes in v2:
> - Don't use struct_size() for now.
> - Update subject line and changelog text.
>
> drivers/acpi/acpica/utids.c | 2 +-
> include/acpi/actypes.h | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/acpica/utids.c b/drivers/acpi/acpica/utids.c
> index 3bb06935a2ad3..225f3c60203c7 100644
> --- a/drivers/acpi/acpica/utids.c
> +++ b/drivers/acpi/acpica/utids.c
> @@ -263,7 +263,7 @@ acpi_ut_execute_CID(struct acpi_namespace_node *device_node,
> * 3) Size of the actual CID strings
> */
> cid_list_size = sizeof(struct acpi_pnp_device_id_list) +
> - ((count - 1) * sizeof(struct acpi_pnp_device_id)) +
> + count * sizeof(struct acpi_pnp_device_id) +
> string_area_size;
>
> cid_list = ACPI_ALLOCATE_ZEROED(cid_list_size);
> diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h
> index 4defed58ea338..c7bcda0ad366a 100644
> --- a/include/acpi/actypes.h
> +++ b/include/acpi/actypes.h
> @@ -1145,7 +1145,7 @@ struct acpi_pnp_device_id {
> struct acpi_pnp_device_id_list {
> u32 count; /* Number of IDs in Ids array */
> u32 list_size; /* Size of list, including ID strings */
> - struct acpi_pnp_device_id ids[1]; /* ID array */
> + struct acpi_pnp_device_id ids[]; /* ID array */
> };
>
> /*
> --
> 2.27.0
>
> -----Original Message-----
> From: [email protected] <linux-acpi-
> [email protected]> On Behalf Of Rafael J. Wysocki
> Sent: Wednesday, June 3, 2020 6:04 AM
> To: Gustavo A. R. Silva <[email protected]>; Kaneda, Erik
> <[email protected]>
> Cc: Moore, Robert <[email protected]>; Wysocki, Rafael J
> <[email protected]>; Len Brown <[email protected]>; ACPI Devel
> Maling List <[email protected]>; open list:ACPI COMPONENT
> ARCHITECTURE (ACPICA) <[email protected]>; Linux Kernel Mailing List
> <[email protected]>; Gustavo A. R. Silva
> <[email protected]>
> Subject: Re: [PATCH v2] ACPICA: Replace one-element array with flexible-
> array
>
> On Tue, Jun 2, 2020 at 11:34 PM Gustavo A. R. Silva <[email protected]>
> wrote:
> >
> > The current codebase makes use of one-element arrays in the following
> > form:
> >
> > struct something {
> > int length;
> > u8 data[1];
> > };
> >
> > struct something *instance;
> >
> > instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL);
> > instance->length = size;
> > memcpy(instance->data, source, size);
> >
> > but the preferred mechanism to declare variable-length types such as
> > these ones is a flexible array member[1][2], introduced in C99:
> >
> > struct foo {
> > int stuff;
> > struct boo array[];
> > };
> >
> > By making use of the mechanism above, we will get a compiler warning
> > in case the flexible array does not occur last in the structure, which
> > will help us prevent some kind of undefined behavior bugs from being
> > inadvertently introduced[3] to the codebase from now on.
> >
> > This issue was found with the help of Coccinelle and audited _manually_.
> >
> > [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
> > [2] https://github.com/KSPP/linux/issues/21
> > [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
> >
> > Signed-off-by: Gustavo A. R. Silva <[email protected]>
>
> Erik, can you take this to the upstream, please?
Yes, We'll have to make additional changes to other structures with one-element arrays but we'll get this in time for the upcoming ACPICA release.
Thanks,
Erik
>
> > ---
> > Changes in v2:
> > - Don't use struct_size() for now.
> > - Update subject line and changelog text.
> >
> > drivers/acpi/acpica/utids.c | 2 +-
> > include/acpi/actypes.h | 2 +-
> > 2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/acpi/acpica/utids.c b/drivers/acpi/acpica/utids.c
> > index 3bb06935a2ad3..225f3c60203c7 100644
> > --- a/drivers/acpi/acpica/utids.c
> > +++ b/drivers/acpi/acpica/utids.c
> > @@ -263,7 +263,7 @@ acpi_ut_execute_CID(struct acpi_namespace_node
> *device_node,
> > * 3) Size of the actual CID strings
> > */
> > cid_list_size = sizeof(struct acpi_pnp_device_id_list) +
> > - ((count - 1) * sizeof(struct acpi_pnp_device_id)) +
> > + count * sizeof(struct acpi_pnp_device_id) +
> > string_area_size;
> >
> > cid_list = ACPI_ALLOCATE_ZEROED(cid_list_size);
> > diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h index
> > 4defed58ea338..c7bcda0ad366a 100644
> > --- a/include/acpi/actypes.h
> > +++ b/include/acpi/actypes.h
> > @@ -1145,7 +1145,7 @@ struct acpi_pnp_device_id { struct
> > acpi_pnp_device_id_list {
> > u32 count; /* Number of IDs in Ids array */
> > u32 list_size; /* Size of list, including ID strings */
> > - struct acpi_pnp_device_id ids[1]; /* ID array */
> > + struct acpi_pnp_device_id ids[]; /* ID array */
> > };
> >
> > /*
> > --
> > 2.27.0
> >
> -----Original Message-----
> From: [email protected] <linux-acpi-
> [email protected]> On Behalf Of Kaneda, Erik
> Sent: Wednesday, June 3, 2020 4:13 PM
> To: Rafael J. Wysocki <[email protected]>; Gustavo A. R. Silva
> <[email protected]>
> Cc: Moore, Robert <[email protected]>; Wysocki, Rafael J
> <[email protected]>; Len Brown <[email protected]>; ACPI Devel
> Maling List <[email protected]>; open list:ACPI COMPONENT
> ARCHITECTURE (ACPICA) <[email protected]>; Linux Kernel Mailing List
> <[email protected]>; Gustavo A. R. Silva
> <[email protected]>
> Subject: RE: [PATCH v2] ACPICA: Replace one-element array with flexible-
> array
>
>
>
> > -----Original Message-----
> > From: [email protected] <linux-acpi-
> > [email protected]> On Behalf Of Rafael J. Wysocki
> > Sent: Wednesday, June 3, 2020 6:04 AM
> > To: Gustavo A. R. Silva <[email protected]>; Kaneda, Erik
> > <[email protected]>
> > Cc: Moore, Robert <[email protected]>; Wysocki, Rafael J
> > <[email protected]>; Len Brown <[email protected]>; ACPI Devel
> > Maling List <[email protected]>; open list:ACPI COMPONENT
> > ARCHITECTURE (ACPICA) <[email protected]>; Linux Kernel Mailing List
> > <[email protected]>; Gustavo A. R. Silva
> > <[email protected]>
> > Subject: Re: [PATCH v2] ACPICA: Replace one-element array with
> > flexible- array
> >
> > On Tue, Jun 2, 2020 at 11:34 PM Gustavo A. R. Silva
> > <[email protected]>
> > wrote:
> > >
> > > The current codebase makes use of one-element arrays in the
> > > following
> > > form:
> > >
> > > struct something {
> > > int length;
> > > u8 data[1];
> > > };
> > >
> > > struct something *instance;
> > >
> > > instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL);
> > > instance->length = size;
> > > memcpy(instance->data, source, size);
> > >
> > > but the preferred mechanism to declare variable-length types such as
> > > these ones is a flexible array member[1][2], introduced in C99:
> > >
> > > struct foo {
> > > int stuff;
> > > struct boo array[];
> > > };
> > >
> > > By making use of the mechanism above, we will get a compiler warning
> > > in case the flexible array does not occur last in the structure,
> > > which will help us prevent some kind of undefined behavior bugs from
> > > being inadvertently introduced[3] to the codebase from now on.
> > >
> > > This issue was found with the help of Coccinelle and audited _manually_.
> > >
> > > [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
> > > [2] https://github.com/KSPP/linux/issues/21
> > > [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
> > >
> > > Signed-off-by: Gustavo A. R. Silva <[email protected]>
> >
> > Erik, can you take this to the upstream, please?
> Yes, We'll have to make additional changes to other structures with one-
> element arrays but we'll get this in time for the upcoming ACPICA release.
Pull request available here: https://github.com/acpica/acpica/pull/608
Erik
>
> Thanks,
> Erik
> >
> > > ---
> > > Changes in v2:
> > > - Don't use struct_size() for now.
> > > - Update subject line and changelog text.
> > >
> > > drivers/acpi/acpica/utids.c | 2 +-
> > > include/acpi/actypes.h | 2 +-
> > > 2 files changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/acpi/acpica/utids.c
> > > b/drivers/acpi/acpica/utids.c index 3bb06935a2ad3..225f3c60203c7
> > > 100644
> > > --- a/drivers/acpi/acpica/utids.c
> > > +++ b/drivers/acpi/acpica/utids.c
> > > @@ -263,7 +263,7 @@ acpi_ut_execute_CID(struct
> acpi_namespace_node
> > *device_node,
> > > * 3) Size of the actual CID strings
> > > */
> > > cid_list_size = sizeof(struct acpi_pnp_device_id_list) +
> > > - ((count - 1) * sizeof(struct acpi_pnp_device_id)) +
> > > + count * sizeof(struct acpi_pnp_device_id) +
> > > string_area_size;
> > >
> > > cid_list = ACPI_ALLOCATE_ZEROED(cid_list_size);
> > > diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h index
> > > 4defed58ea338..c7bcda0ad366a 100644
> > > --- a/include/acpi/actypes.h
> > > +++ b/include/acpi/actypes.h
> > > @@ -1145,7 +1145,7 @@ struct acpi_pnp_device_id { struct
> > > acpi_pnp_device_id_list {
> > > u32 count; /* Number of IDs in Ids array */
> > > u32 list_size; /* Size of list, including ID strings */
> > > - struct acpi_pnp_device_id ids[1]; /* ID array */
> > > + struct acpi_pnp_device_id ids[]; /* ID array */
> > > };
> > >
> > > /*
> > > --
> > > 2.27.0
> > >