[PATCH v2][next] firewire: core: avoid -Wflex-array-member-not-at-end warning

Gustavo A. R. Silva
2025-03-13T22:28:21Z

Use the `DEFINE_RAW_FLEX()` helper for an on-stack definition of
a flexible structure where the size of the flexible-array member
is known at compile-time, and refactor the rest of the code,
accordingly.

So, with these changes, fix the following warning:

drivers/firewire/core-cdev.c:1141:38: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Changes in v2:
- Adjust COUNT argument for DEFINE_RAW_FLEX() to 64. (Takashi)

v1:
- Link: https://lore.kernel.org/linux-hardening/Z9AA9tAbcIcz6BMO@kspp/

drivers/firewire/core-cdev.c | 42 ++++++++++++++++--------------------
1 file changed, 19 insertions(+), 23 deletions(-)

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index b360dca2c69e..bd04980009a4 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -1137,10 +1137,7 @@ static int ioctl_queue_iso(struct client *client, union ioctl_arg *arg)
unsigned long payload, buffer_end, transmit_header_bytes = 0;
u32 control;
int count;
- struct {
- struct fw_iso_packet packet;
- u8 header[256];
- } u;
+ DEFINE_RAW_FLEX(struct fw_iso_packet, u, header, 64);

if (ctx == NULL || a->handle != 0)
return -EINVAL;
@@ -1172,29 +1169,29 @@ static int ioctl_queue_iso(struct client *client, union ioctl_arg *arg)
while (p < end) {
if (get_user(control, &p->control))
return -EFAULT;
- u.packet.payload_length = GET_PAYLOAD_LENGTH(control);
- u.packet.interrupt = GET_INTERRUPT(control);
- u.packet.skip = GET_SKIP(control);
- u.packet.tag = GET_TAG(control);
- u.packet.sy = GET_SY(control);
- u.packet.header_length = GET_HEADER_LENGTH(control);
+ u->payload_length = GET_PAYLOAD_LENGTH(control);
+ u->interrupt = GET_INTERRUPT(control);
+ u->skip = GET_SKIP(control);
+ u->tag = GET_TAG(control);
+ u->sy = GET_SY(control);
+ u->header_length = GET_HEADER_LENGTH(control);

switch (ctx->type) {
case FW_ISO_CONTEXT_TRANSMIT:
- if (u.packet.header_length & 3)
+ if (u->header_length & 3)
return -EINVAL;
- transmit_header_bytes = u.packet.header_length;
+ transmit_header_bytes = u->header_length;
break;

case FW_ISO_CONTEXT_RECEIVE:
- if (u.packet.header_length == 0 ||
- u.packet.header_length % ctx->header_size != 0)
+ if (u->header_length == 0 ||
+ u->header_length % ctx->header_size != 0)
return -EINVAL;
break;

case FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL:
- if (u.packet.payload_length == 0 ||
- u.packet.payload_length & 3)
+ if (u->payload_length == 0 ||
+ u->payload_length & 3)
return -EINVAL;
break;
}
@@ -1204,20 +1201,19 @@ static int ioctl_queue_iso(struct client *client, union ioctl_arg *arg)
if (next > end)
return -EINVAL;
if (copy_from_user
- (u.packet.header, p->header, transmit_header_bytes))
+ (u->header, p->header, transmit_header_bytes))
return -EFAULT;
- if (u.packet.skip && ctx->type == FW_ISO_CONTEXT_TRANSMIT &&
- u.packet.header_length + u.packet.payload_length > 0)
+ if (u->skip && ctx->type == FW_ISO_CONTEXT_TRANSMIT &&
+ u->header_length + u->payload_length > 0)
return -EINVAL;
- if (payload + u.packet.payload_length > buffer_end)
+ if (payload + u->payload_length > buffer_end)
return -EINVAL;

- if (fw_iso_context_queue(ctx, &u.packet,
- &client->buffer, payload))
+ if (fw_iso_context_queue(ctx, u, &client->buffer, payload))
break;

p = next;
- payload += u.packet.payload_length;
+ payload += u->payload_length;
count++;
}
fw_iso_context_queue_flush(ctx);
--
2.43.0