[PATCH][next] RDMA/uverbs: Avoid -Wflex-array-member-not-at-end warnings

Gustavo A. R. Silva
2024-03-01T18:37:47Z

-Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
ready to enable it globally.

There are currently a couple of objects (`alloc_head` and `bundle`) in
`struct bundle_priv` that contain a couple of flexible structures:

struct bundle_priv {
/* Must be first */
struct bundle_alloc_head alloc_head;

...

/*
* Must be last. bundle ends in a flex array which overlaps
* internal_buffer.
*/
struct uverbs_attr_bundle bundle;
u64 internal_buffer[32];
};

So, in order to avoid ending up with a couple of flexible-array members
in the middle of a struct, we use the `struct_group_tagged()` helper to
separate the flexible array from the rest of the members in the flexible
structures:

struct uverbs_attr_bundle {
struct_group_tagged(uverbs_attr_bundle_hdr, hdr,
... the rest of the members
);
struct uverbs_attr attrs[];
};

With the change described above, we now declare objects of the type of
the tagged struct without embedding flexible arrays in the middle of
another struct:

struct bundle_priv {
/* Must be first */
struct bundle_alloc_head_hdr alloc_head;

...

struct uverbs_attr_bundle_hdr bundle;
u64 internal_buffer[32];
};

We also use `container_of()` whenever we need to retrieve a pointer
to the flexible structures.

Notice that the `bundle_size` computed in `uapi_compute_bundle_size()`
remains the same.

So, with these changes, fix the following warnings:

drivers/infiniband/core/uverbs_ioctl.c:45:34: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
45 | struct bundle_alloc_head alloc_head;
| ^~~~~~~~~~
drivers/infiniband/core/uverbs_ioctl.c:67:35: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
67 | struct uverbs_attr_bundle bundle;
| ^~~~~~

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
drivers/infiniband/core/uverbs_ioctl.c | 78 +++++++++++++++-----------
include/rdma/uverbs_ioctl.h | 14 +++--
2 files changed, 53 insertions(+), 39 deletions(-)

diff --git a/drivers/infiniband/core/uverbs_ioctl.c b/drivers/infiniband/core/uverbs_ioctl.c
index d9799706c58e..f80da6a67e24 100644
--- a/drivers/infiniband/core/uverbs_ioctl.c
+++ b/drivers/infiniband/core/uverbs_ioctl.c
@@ -36,13 +36,15 @@
#include "uverbs.h"

struct bundle_alloc_head {
- struct bundle_alloc_head *next;
+ struct_group_tagged(bundle_alloc_head_hdr, hdr,
+ struct bundle_alloc_head *next;
+ );
u8 data[];
};

struct bundle_priv {
/* Must be first */
- struct bundle_alloc_head alloc_head;
+ struct bundle_alloc_head_hdr alloc_head;
struct bundle_alloc_head *allocated_mem;
size_t internal_avail;
size_t internal_used;
@@ -64,7 +66,7 @@ struct bundle_priv {
* Must be last. bundle ends in a flex array which overlaps
* internal_buffer.
*/
- struct uverbs_attr_bundle bundle;
+ struct uverbs_attr_bundle_hdr bundle;
u64 internal_buffer[32];
};

@@ -77,9 +79,10 @@ void uapi_compute_bundle_size(struct uverbs_api_ioctl_method *method_elm,
unsigned int num_attrs)
{
struct bundle_priv *pbundle;
+ struct uverbs_attr_bundle *bundle;
size_t bundle_size =
offsetof(struct bundle_priv, internal_buffer) +
- sizeof(*pbundle->bundle.attrs) * method_elm->key_bitmap_len +
+ sizeof(*bundle->attrs) * method_elm->key_bitmap_len +
sizeof(*pbundle->uattrs) * num_attrs;

method_elm->use_stack = bundle_size <= sizeof(*pbundle);
@@ -107,7 +110,7 @@ __malloc void *_uverbs_alloc(struct uverbs_attr_bundle *bundle, size_t size,
gfp_t flags)
{
struct bundle_priv *pbundle =
- container_of(bundle, struct bundle_priv, bundle);
+ container_of(&bundle->hdr, struct bundle_priv, bundle);
size_t new_used;
void *res;

@@ -149,7 +152,7 @@ static int uverbs_set_output(const struct uverbs_attr_bundle *bundle,
const struct uverbs_attr *attr)
{
struct bundle_priv *pbundle =
- container_of(bundle, struct bundle_priv, bundle);
+ container_of(&bundle->hdr, struct bundle_priv, bundle);
u16 flags;

flags = pbundle->uattrs[attr->ptr_attr.uattr_idx].flags |
@@ -166,6 +169,8 @@ static int uverbs_process_idrs_array(struct bundle_priv *pbundle,
struct ib_uverbs_attr *uattr,
u32 attr_bkey)
{
+ struct uverbs_attr_bundle *bundle =
+ container_of(&pbundle->bundle, struct uverbs_attr_bundle, hdr);
const struct uverbs_attr_spec *spec = &attr_uapi->spec;
size_t array_len;
u32 *idr_vals;
@@ -184,7 +189,7 @@ static int uverbs_process_idrs_array(struct bundle_priv *pbundle,
return -EINVAL;

attr->uobjects =
- uverbs_alloc(&pbundle->bundle,
+ uverbs_alloc(bundle,
array_size(array_len, sizeof(*attr->uobjects)));
if (IS_ERR(attr->uobjects))
return PTR_ERR(attr->uobjects);
@@ -209,7 +214,7 @@ static int uverbs_process_idrs_array(struct bundle_priv *pbundle,
for (i = 0; i != array_len; i++) {
attr->uobjects[i] = uverbs_get_uobject_from_file(
spec->u2.objs_arr.obj_type, spec->u2.objs_arr.access,
- idr_vals[i], &pbundle->bundle);
+ idr_vals[i], bundle);
if (IS_ERR(attr->uobjects[i])) {
ret = PTR_ERR(attr->uobjects[i]);
break;
@@ -240,7 +245,9 @@ static int uverbs_process_attr(struct bundle_priv *pbundle,
struct ib_uverbs_attr *uattr, u32 attr_bkey)
{
const struct uverbs_attr_spec *spec = &attr_uapi->spec;
- struct uverbs_attr *e = &pbundle->bundle.attrs[attr_bkey];
+ struct uverbs_attr_bundle *bundle =
+ container_of(&pbundle->bundle, struct uverbs_attr_bundle, hdr);
+ struct uverbs_attr *e = &bundle->attrs[attr_bkey];
const struct uverbs_attr_spec *val_spec = spec;
struct uverbs_obj_attr *o_attr;

@@ -288,7 +295,7 @@ static int uverbs_process_attr(struct bundle_priv *pbundle,
if (val_spec->alloc_and_copy && !uverbs_attr_ptr_is_inline(e)) {
void *p;

- p = uverbs_alloc(&pbundle->bundle, uattr->len);
+ p = uverbs_alloc(bundle, uattr->len);
if (IS_ERR(p))
return PTR_ERR(p);

@@ -321,7 +328,7 @@ static int uverbs_process_attr(struct bundle_priv *pbundle,
*/
o_attr->uobject = uverbs_get_uobject_from_file(
spec->u.obj.obj_type, spec->u.obj.access,
- uattr->data_s64, &pbundle->bundle);
+ uattr->data_s64, bundle);
if (IS_ERR(o_attr->uobject))
return PTR_ERR(o_attr->uobject);
__set_bit(attr_bkey, pbundle->uobj_finalize);
@@ -422,6 +429,8 @@ static int ib_uverbs_run_method(struct bundle_priv *pbundle,
unsigned int num_attrs)
{
int (*handler)(struct uverbs_attr_bundle *attrs);
+ struct uverbs_attr_bundle *bundle =
+ container_of(&pbundle->bundle, struct uverbs_attr_bundle, hdr);
size_t uattrs_size = array_size(sizeof(*pbundle->uattrs), num_attrs);
unsigned int destroy_bkey = pbundle->method_elm->destroy_bkey;
unsigned int i;
@@ -434,7 +443,7 @@ static int ib_uverbs_run_method(struct bundle_priv *pbundle,
if (!handler)
return -EIO;

- pbundle->uattrs = uverbs_alloc(&pbundle->bundle, uattrs_size);
+ pbundle->uattrs = uverbs_alloc(bundle, uattrs_size);
if (IS_ERR(pbundle->uattrs))
return PTR_ERR(pbundle->uattrs);
if (copy_from_user(pbundle->uattrs, pbundle->user_attrs, uattrs_size))
@@ -453,25 +462,23 @@ static int ib_uverbs_run_method(struct bundle_priv *pbundle,
return -EINVAL;

if (pbundle->method_elm->has_udata)
- uverbs_fill_udata(&pbundle->bundle,
- &pbundle->bundle.driver_udata,
+ uverbs_fill_udata(bundle, &pbundle->bundle.driver_udata,
UVERBS_ATTR_UHW_IN, UVERBS_ATTR_UHW_OUT);
else
pbundle->bundle.driver_udata = (struct ib_udata){};

if (destroy_bkey != UVERBS_API_ATTR_BKEY_LEN) {
- struct uverbs_obj_attr *destroy_attr =
- &pbundle->bundle.attrs[destroy_bkey].obj_attr;
+ struct uverbs_obj_attr *destroy_attr = &bundle->attrs[destroy_bkey].obj_attr;

- ret = uobj_destroy(destroy_attr->uobject, &pbundle->bundle);
+ ret = uobj_destroy(destroy_attr->uobject, bundle);
if (ret)
return ret;
__clear_bit(destroy_bkey, pbundle->uobj_finalize);

- ret = handler(&pbundle->bundle);
+ ret = handler(bundle);
uobj_put_destroy(destroy_attr->uobject);
} else {
- ret = handler(&pbundle->bundle);
+ ret = handler(bundle);
}

/*
@@ -481,10 +488,10 @@ static int ib_uverbs_run_method(struct bundle_priv *pbundle,
*/
if (!ret && pbundle->method_elm->has_udata) {
const struct uverbs_attr *attr =
- uverbs_attr_get(&pbundle->bundle, UVERBS_ATTR_UHW_OUT);
+ uverbs_attr_get(bundle, UVERBS_ATTR_UHW_OUT);

if (!IS_ERR(attr))
- ret = uverbs_set_output(&pbundle->bundle, attr);
+ ret = uverbs_set_output(bundle, attr);
}

/*
@@ -501,6 +508,8 @@ static int ib_uverbs_run_method(struct bundle_priv *pbundle,
static void bundle_destroy(struct bundle_priv *pbundle, bool commit)
{
unsigned int key_bitmap_len = pbundle->method_elm->key_bitmap_len;
+ struct uverbs_attr_bundle *bundle =
+ container_of(&pbundle->bundle, struct uverbs_attr_bundle, hdr);
struct bundle_alloc_head *memblock;
unsigned int i;

@@ -508,20 +517,19 @@ static void bundle_destroy(struct bundle_priv *pbundle, bool commit)
i = -1;
while ((i = find_next_bit(pbundle->uobj_finalize, key_bitmap_len,
i + 1)) < key_bitmap_len) {
- struct uverbs_attr *attr = &pbundle->bundle.attrs[i];
+ struct uverbs_attr *attr = &bundle->attrs[i];

uverbs_finalize_object(
attr->obj_attr.uobject,
attr->obj_attr.attr_elm->spec.u.obj.access,
test_bit(i, pbundle->uobj_hw_obj_valid),
- commit,
- &pbundle->bundle);
+ commit, bundle);
}

i = -1;
while ((i = find_next_bit(pbundle->spec_finalize, key_bitmap_len,
i + 1)) < key_bitmap_len) {
- struct uverbs_attr *attr = &pbundle->bundle.attrs[i];
+ struct uverbs_attr *attr = &bundle->attrs[i];
const struct uverbs_api_attr *attr_uapi;
void __rcu **slot;

@@ -535,7 +543,7 @@ static void bundle_destroy(struct bundle_priv *pbundle, bool commit)

if (attr_uapi->spec.type == UVERBS_ATTR_TYPE_IDRS_ARRAY) {
uverbs_free_idrs_array(attr_uapi, &attr->objs_arr_attr,
- commit, &pbundle->bundle);
+ commit, bundle);
}
}

@@ -578,7 +586,8 @@ static int ib_uverbs_cmd_verbs(struct ib_uverbs_file *ufile,
method_elm->bundle_size -
offsetof(struct bundle_priv, internal_buffer);
pbundle->alloc_head.next = NULL;
- pbundle->allocated_mem = &pbundle->alloc_head;
+ pbundle->allocated_mem = container_of(&pbundle->alloc_head,
+ struct bundle_alloc_head, hdr);
} else {
pbundle = &onstack;
pbundle->internal_avail = sizeof(pbundle->internal_buffer);
@@ -596,8 +605,9 @@ static int ib_uverbs_cmd_verbs(struct ib_uverbs_file *ufile,
pbundle->user_attrs = user_attrs;

pbundle->internal_used = ALIGN(pbundle->method_elm->key_bitmap_len *
- sizeof(*pbundle->bundle.attrs),
- sizeof(*pbundle->internal_buffer));
+ sizeof(*container_of(&pbundle->bundle,
+ struct uverbs_attr_bundle, hdr)->attrs),
+ sizeof(*pbundle->internal_buffer));
memset(pbundle->bundle.attr_present, 0,
sizeof(pbundle->bundle.attr_present));
memset(pbundle->uobj_finalize, 0, sizeof(pbundle->uobj_finalize));
@@ -700,11 +710,13 @@ void uverbs_fill_udata(struct uverbs_attr_bundle *bundle,
unsigned int attr_out)
{
struct bundle_priv *pbundle =
- container_of(bundle, struct bundle_priv, bundle);
+ container_of(&bundle->hdr, struct bundle_priv, bundle);
+ struct uverbs_attr_bundle *bundle_aux =
+ container_of(&pbundle->bundle, struct uverbs_attr_bundle, hdr);
const struct uverbs_attr *in =
- uverbs_attr_get(&pbundle->bundle, attr_in);
+ uverbs_attr_get(bundle_aux, attr_in);
const struct uverbs_attr *out =
- uverbs_attr_get(&pbundle->bundle, attr_out);
+ uverbs_attr_get(bundle_aux, attr_out);

if (!IS_ERR(in)) {
udata->inlen = in->ptr_attr.len;
@@ -829,7 +841,7 @@ void uverbs_finalize_uobj_create(const struct uverbs_attr_bundle *bundle,
u16 idx)
{
struct bundle_priv *pbundle =
- container_of(bundle, struct bundle_priv, bundle);
+ container_of(&bundle->hdr, struct bundle_priv, bundle);

__set_bit(uapi_bkey_attr(uapi_key_attr(idx)),
pbundle->uobj_hw_obj_valid);
diff --git a/include/rdma/uverbs_ioctl.h b/include/rdma/uverbs_ioctl.h
index 06287de69cd2..e6c0de227fad 100644
--- a/include/rdma/uverbs_ioctl.h
+++ b/include/rdma/uverbs_ioctl.h
@@ -629,12 +629,14 @@ struct uverbs_attr {
};

struct uverbs_attr_bundle {
- struct ib_udata driver_udata;
- struct ib_udata ucore;
- struct ib_uverbs_file *ufile;
- struct ib_ucontext *context;
- struct ib_uobject *uobject;
- DECLARE_BITMAP(attr_present, UVERBS_API_ATTR_BKEY_LEN);
+ struct_group_tagged(uverbs_attr_bundle_hdr, hdr,
+ struct ib_udata driver_udata;
+ struct ib_udata ucore;
+ struct ib_uverbs_file *ufile;
+ struct ib_ucontext *context;
+ struct ib_uobject *uobject;
+ DECLARE_BITMAP(attr_present, UVERBS_API_ATTR_BKEY_LEN);
+ );
struct uverbs_attr attrs[];
};

--
2.34.1