[PATCH v2][next] Bluetooth: L2CAP: Avoid -Wflex-array-member-not-at-end warnings
From: Gustavo A. R. Silva
Date: Wed Mar 27 2024 - 12:24:06 EST
-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 (`req` and `rsp`), in a couple
of structures, that contain flexible structures (`struct l2cap_ecred_conn_req`
and `struct l2cap_ecred_conn_rsp`), for example:
struct l2cap_ecred_rsp_data {
struct {
struct l2cap_ecred_conn_rsp rsp;
__le16 scid[L2CAP_ECRED_MAX_CID];
} __packed pdu;
int count;
};
in the struct above, `struct l2cap_ecred_conn_rsp` is a flexible
structure:
struct l2cap_ecred_conn_rsp {
__le16 mtu;
__le16 mps;
__le16 credits;
__le16 result;
__le16 dcid[];
};
So, in order to avoid ending up with a flexible-array member in the
middle of another structure, we use the `struct_group_tagged()` (and
`__struct_group()` when the flexible structure is `__packed`) helper
to separate the flexible array from the rest of the members in the
flexible structure:
struct l2cap_ecred_conn_rsp {
struct_group_tagged(l2cap_ecred_conn_rsp_hdr, hdr,
... the rest of members
);
__le16 dcid[];
};
With the change described above, we now declare objects of the type of
the tagged struct, in this example `struct l2cap_ecred_conn_rsp_hdr`,
without embedding flexible arrays in the middle of other structures:
struct l2cap_ecred_rsp_data {
struct {
struct l2cap_ecred_conn_rsp_hdr rsp;
__le16 scid[L2CAP_ECRED_MAX_CID];
} __packed pdu;
int count;
};
Also, when the flexible-array member needs to be accessed, we use
`container_of()` to retrieve a pointer to the flexible structure.
We also use the `DEFINE_RAW_FLEX()` helper for a couple of on-stack
definitions of a flexible structure where the size of the flexible-array
member is known at compile-time.
So, with these changes, fix the following warnings:
net/bluetooth/l2cap_core.c:1260:45: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
net/bluetooth/l2cap_core.c:3740:45: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
net/bluetooth/l2cap_core.c:4999:45: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
net/bluetooth/l2cap_core.c:7116:47: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
Link: https://github.com/KSPP/linux/issues/202
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
---
Changes in v2:
- Add a couple of code comments.
v1:
- Link: https://lore.kernel.org/linux-hardening/ZgMpynzZ8FltPCi3@neat/
Hi!
I wonder if `struct l2cap_ecred_conn_rsp` should also be `__packed`.
Thanks
- Gustavo
include/net/bluetooth/l2cap.h | 22 +++++++++++------
net/bluetooth/l2cap_core.c | 46 ++++++++++++++++-------------------
2 files changed, 35 insertions(+), 33 deletions(-)
diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
index a4278aa618ab..7d4a3e766e7b 100644
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -463,18 +463,24 @@ struct l2cap_le_credits {
#define L2CAP_ECRED_MAX_CID 5
struct l2cap_ecred_conn_req {
- __le16 psm;
- __le16 mtu;
- __le16 mps;
- __le16 credits;
+ /* New members must be added within the struct_group() macro below. */
+ __struct_group(l2cap_ecred_conn_req_hdr, hdr, __packed,
+ __le16 psm;
+ __le16 mtu;
+ __le16 mps;
+ __le16 credits;
+ );
__le16 scid[];
} __packed;
struct l2cap_ecred_conn_rsp {
- __le16 mtu;
- __le16 mps;
- __le16 credits;
- __le16 result;
+ /* New members must be added within the struct_group() macro below. */
+ struct_group_tagged(l2cap_ecred_conn_rsp_hdr, hdr,
+ __le16 mtu;
+ __le16 mps;
+ __le16 credits;
+ __le16 result;
+ );
__le16 dcid[];
};
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 467b242d8be0..bf087eca489e 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1257,7 +1257,7 @@ static void l2cap_le_connect(struct l2cap_chan *chan)
struct l2cap_ecred_conn_data {
struct {
- struct l2cap_ecred_conn_req req;
+ struct l2cap_ecred_conn_req_hdr req;
__le16 scid[5];
} __packed pdu;
struct l2cap_chan *chan;
@@ -3737,7 +3737,7 @@ static void l2cap_ecred_list_defer(struct l2cap_chan *chan, void *data)
struct l2cap_ecred_rsp_data {
struct {
- struct l2cap_ecred_conn_rsp rsp;
+ struct l2cap_ecred_conn_rsp_hdr rsp;
__le16 scid[L2CAP_ECRED_MAX_CID];
} __packed pdu;
int count;
@@ -3746,6 +3746,8 @@ struct l2cap_ecred_rsp_data {
static void l2cap_ecred_rsp_defer(struct l2cap_chan *chan, void *data)
{
struct l2cap_ecred_rsp_data *rsp = data;
+ struct l2cap_ecred_conn_rsp *rsp_flex =
+ container_of(&rsp->pdu.rsp, struct l2cap_ecred_conn_rsp, hdr);
if (test_bit(FLAG_ECRED_CONN_REQ_SENT, &chan->flags))
return;
@@ -3755,7 +3757,7 @@ static void l2cap_ecred_rsp_defer(struct l2cap_chan *chan, void *data)
/* Include all channels pending with the same ident */
if (!rsp->pdu.rsp.result)
- rsp->pdu.rsp.dcid[rsp->count++] = cpu_to_le16(chan->scid);
+ rsp_flex->dcid[rsp->count++] = cpu_to_le16(chan->scid);
else
l2cap_chan_del(chan, ECONNRESET);
}
@@ -4995,10 +4997,7 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
u8 *data)
{
struct l2cap_ecred_conn_req *req = (void *) data;
- struct {
- struct l2cap_ecred_conn_rsp rsp;
- __le16 dcid[L2CAP_ECRED_MAX_CID];
- } __packed pdu;
+ DEFINE_RAW_FLEX(struct l2cap_ecred_conn_rsp, pdu, dcid, L2CAP_ECRED_MAX_CID);
struct l2cap_chan *chan, *pchan;
u16 mtu, mps;
__le16 psm;
@@ -5017,7 +5016,7 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
cmd_len -= sizeof(*req);
num_scid = cmd_len / sizeof(u16);
- if (num_scid > ARRAY_SIZE(pdu.dcid)) {
+ if (num_scid > L2CAP_ECRED_MAX_CID) {
result = L2CAP_CR_LE_INVALID_PARAMS;
goto response;
}
@@ -5046,7 +5045,7 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
BT_DBG("psm 0x%2.2x mtu %u mps %u", __le16_to_cpu(psm), mtu, mps);
- memset(&pdu, 0, sizeof(pdu));
+ memset(pdu, 0, sizeof(*pdu));
/* Check if we have socket listening on psm */
pchan = l2cap_global_chan_by_psm(BT_LISTEN, psm, &conn->hcon->src,
@@ -5072,8 +5071,8 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
BT_DBG("scid[%d] 0x%4.4x", i, scid);
- pdu.dcid[i] = 0x0000;
- len += sizeof(*pdu.dcid);
+ pdu->dcid[i] = 0x0000;
+ len += sizeof(*pdu->dcid);
/* Check for valid dynamic CID range */
if (scid < L2CAP_CID_DYN_START || scid > L2CAP_CID_LE_DYN_END) {
@@ -5107,13 +5106,13 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
l2cap_ecred_init(chan, __le16_to_cpu(req->credits));
/* Init response */
- if (!pdu.rsp.credits) {
- pdu.rsp.mtu = cpu_to_le16(chan->imtu);
- pdu.rsp.mps = cpu_to_le16(chan->mps);
- pdu.rsp.credits = cpu_to_le16(chan->rx_credits);
+ if (!pdu->credits) {
+ pdu->mtu = cpu_to_le16(chan->imtu);
+ pdu->mps = cpu_to_le16(chan->mps);
+ pdu->credits = cpu_to_le16(chan->rx_credits);
}
- pdu.dcid[i] = cpu_to_le16(chan->scid);
+ pdu->dcid[i] = cpu_to_le16(chan->scid);
__set_chan_timer(chan, chan->ops->get_sndtimeo(chan));
@@ -5135,13 +5134,13 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
l2cap_chan_put(pchan);
response:
- pdu.rsp.result = cpu_to_le16(result);
+ pdu->result = cpu_to_le16(result);
if (defer)
return 0;
l2cap_send_cmd(conn, cmd->ident, L2CAP_ECRED_CONN_RSP,
- sizeof(pdu.rsp) + len, &pdu);
+ sizeof(*pdu) + len, pdu);
return 0;
}
@@ -7112,14 +7111,11 @@ EXPORT_SYMBOL_GPL(l2cap_chan_connect);
static void l2cap_ecred_reconfigure(struct l2cap_chan *chan)
{
struct l2cap_conn *conn = chan->conn;
- struct {
- struct l2cap_ecred_reconf_req req;
- __le16 scid;
- } pdu;
+ DEFINE_RAW_FLEX(struct l2cap_ecred_reconf_req, pdu, scid, 1);
- pdu.req.mtu = cpu_to_le16(chan->imtu);
- pdu.req.mps = cpu_to_le16(chan->mps);
- pdu.scid = cpu_to_le16(chan->scid);
+ pdu->mtu = cpu_to_le16(chan->imtu);
+ pdu->mps = cpu_to_le16(chan->mps);
+ pdu->scid[0] = cpu_to_le16(chan->scid);
chan->ident = l2cap_get_ident(conn);
--
2.34.1