include/net/bluetooth/hci.h | 8 ++-- net/bluetooth/hci_event.c | 3 +- net/bluetooth/hci_sync.c | 84 +++++++++++++++---------------------- 3 files changed, 40 insertions(+), 55 deletions(-)
Prepare for the coming implementation by GCC and Clang of the
__counted_by attribute. Flexible array members annotated with
__counted_by can have their accesses bounds-checked at run-time
via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE
(for strcpy/memcpy-family functions).
Also, -Wflex-array-member-not-at-end is coming in GCC-14, and we are
getting ready to enable it globally.
So, use the `DEFINE_FLEX()` helper for multiple on-stack definitions
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.
Notice that, due to the use of `__counted_by()` in `struct
hci_cp_le_create_cis`, the for loop in function `hci_cs_le_create_cis()`
had to be modified. Once the index `i`, through which `cp->cis[i]` is
accessed, falls in the interval [0, cp->num_cis), `cp->num_cis` cannot
be decremented all the way down to zero while accessing `cp->cis[]`:
net/bluetooth/hci_event.c:4310:
4310 for (i = 0; cp->num_cis; cp->num_cis--, i++) {
...
4314 handle = __le16_to_cpu(cp->cis[i].cis_handle);
otherwise, only half (one iteration before `cp->num_cis == i`) or half
plus one (one iteration before `cp->num_cis < i`) of the items in the
array will be accessed before running into an out-of-bounds issue. So,
in order to avoid this, set `cp->num_cis` to zero just after the for
loop.
Also, make use of `aux_num_cis` variable to update `cmd->num_cis` after
a `list_for_each_entry_rcu()` loop.
With these changes, fix the following warnings:
net/bluetooth/hci_sync.c:1239:56: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
net/bluetooth/hci_sync.c:1415:51: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
net/bluetooth/hci_sync.c:1731:51: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
net/bluetooth/hci_sync.c:6497:45: 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@kernel.org>
---
Changes in v2:
- Update `cmd->num_cis` after `list_for_each_entry_rcu()` loop.
v1:
- Link: https://lore.kernel.org/linux-hardening/ZiwqqZCa7PK9bzCX@neat/
include/net/bluetooth/hci.h | 8 ++--
net/bluetooth/hci_event.c | 3 +-
net/bluetooth/hci_sync.c | 84 +++++++++++++++----------------------
3 files changed, 40 insertions(+), 55 deletions(-)
diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index fe23e862921d..c4c6b8810701 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -2026,7 +2026,7 @@ struct hci_cp_le_set_ext_adv_data {
__u8 operation;
__u8 frag_pref;
__u8 length;
- __u8 data[];
+ __u8 data[] __counted_by(length);
} __packed;
#define HCI_OP_LE_SET_EXT_SCAN_RSP_DATA 0x2038
@@ -2035,7 +2035,7 @@ struct hci_cp_le_set_ext_scan_rsp_data {
__u8 operation;
__u8 frag_pref;
__u8 length;
- __u8 data[];
+ __u8 data[] __counted_by(length);
} __packed;
#define HCI_OP_LE_SET_EXT_ADV_ENABLE 0x2039
@@ -2061,7 +2061,7 @@ struct hci_cp_le_set_per_adv_data {
__u8 handle;
__u8 operation;
__u8 length;
- __u8 data[];
+ __u8 data[] __counted_by(length);
} __packed;
#define HCI_OP_LE_SET_PER_ADV_ENABLE 0x2040
@@ -2162,7 +2162,7 @@ struct hci_cis {
struct hci_cp_le_create_cis {
__u8 num_cis;
- struct hci_cis cis[];
+ struct hci_cis cis[] __counted_by(num_cis);
} __packed;
#define HCI_OP_LE_REMOVE_CIG 0x2065
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 9a38e155537e..9a7ca084302e 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4307,7 +4307,7 @@ static void hci_cs_le_create_cis(struct hci_dev *hdev, u8 status)
hci_dev_lock(hdev);
/* Remove connection if command failed */
- for (i = 0; cp->num_cis; cp->num_cis--, i++) {
+ for (i = 0; i < cp->num_cis; i++) {
struct hci_conn *conn;
u16 handle;
@@ -4323,6 +4323,7 @@ static void hci_cs_le_create_cis(struct hci_dev *hdev, u8 status)
hci_conn_del(conn);
}
}
+ cp->num_cis = 0;
if (pending)
hci_le_create_cis_pending(hdev);
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 9092b4d59545..6e15594d3565 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -1235,31 +1235,27 @@ int hci_setup_ext_adv_instance_sync(struct hci_dev *hdev, u8 instance)
static int hci_set_ext_scan_rsp_data_sync(struct hci_dev *hdev, u8 instance)
{
- struct {
- struct hci_cp_le_set_ext_scan_rsp_data cp;
- u8 data[HCI_MAX_EXT_AD_LENGTH];
- } pdu;
+ DEFINE_FLEX(struct hci_cp_le_set_ext_scan_rsp_data, pdu, data, length,
+ HCI_MAX_EXT_AD_LENGTH);
u8 len;
struct adv_info *adv = NULL;
int err;
- memset(&pdu, 0, sizeof(pdu));
-
if (instance) {
adv = hci_find_adv_instance(hdev, instance);
if (!adv || !adv->scan_rsp_changed)
return 0;
}
- len = eir_create_scan_rsp(hdev, instance, pdu.data);
+ len = eir_create_scan_rsp(hdev, instance, pdu->data);
- pdu.cp.handle = instance;
- pdu.cp.length = len;
- pdu.cp.operation = LE_SET_ADV_DATA_OP_COMPLETE;
- pdu.cp.frag_pref = LE_SET_ADV_DATA_NO_FRAG;
+ pdu->handle = instance;
+ pdu->length = len;
+ pdu->operation = LE_SET_ADV_DATA_OP_COMPLETE;
+ pdu->frag_pref = LE_SET_ADV_DATA_NO_FRAG;
err = __hci_cmd_sync_status(hdev, HCI_OP_LE_SET_EXT_SCAN_RSP_DATA,
- sizeof(pdu.cp) + len, &pdu.cp,
+ struct_size(pdu, data, len), pdu,
HCI_CMD_TIMEOUT);
if (err)
return err;
@@ -1267,7 +1263,7 @@ static int hci_set_ext_scan_rsp_data_sync(struct hci_dev *hdev, u8 instance)
if (adv) {
adv->scan_rsp_changed = false;
} else {
- memcpy(hdev->scan_rsp_data, pdu.data, len);
+ memcpy(hdev->scan_rsp_data, pdu->data, len);
hdev->scan_rsp_data_len = len;
}
@@ -1411,14 +1407,10 @@ static int hci_set_per_adv_params_sync(struct hci_dev *hdev, u8 instance,
static int hci_set_per_adv_data_sync(struct hci_dev *hdev, u8 instance)
{
- struct {
- struct hci_cp_le_set_per_adv_data cp;
- u8 data[HCI_MAX_PER_AD_LENGTH];
- } pdu;
+ DEFINE_FLEX(struct hci_cp_le_set_per_adv_data, pdu, data, length,
+ HCI_MAX_PER_AD_LENGTH);
u8 len;
- memset(&pdu, 0, sizeof(pdu));
-
if (instance) {
struct adv_info *adv = hci_find_adv_instance(hdev, instance);
@@ -1426,14 +1418,14 @@ static int hci_set_per_adv_data_sync(struct hci_dev *hdev, u8 instance)
return 0;
}
- len = eir_create_per_adv_data(hdev, instance, pdu.data);
+ len = eir_create_per_adv_data(hdev, instance, pdu->data);
- pdu.cp.length = len;
- pdu.cp.handle = instance;
- pdu.cp.operation = LE_SET_ADV_DATA_OP_COMPLETE;
+ pdu->length = len;
+ pdu->handle = instance;
+ pdu->operation = LE_SET_ADV_DATA_OP_COMPLETE;
return __hci_cmd_sync_status(hdev, HCI_OP_LE_SET_PER_ADV_DATA,
- sizeof(pdu.cp) + len, &pdu,
+ struct_size(pdu, data, len), pdu,
HCI_CMD_TIMEOUT);
}
@@ -1727,31 +1719,27 @@ int hci_le_terminate_big_sync(struct hci_dev *hdev, u8 handle, u8 reason)
static int hci_set_ext_adv_data_sync(struct hci_dev *hdev, u8 instance)
{
- struct {
- struct hci_cp_le_set_ext_adv_data cp;
- u8 data[HCI_MAX_EXT_AD_LENGTH];
- } pdu;
+ DEFINE_FLEX(struct hci_cp_le_set_ext_adv_data, pdu, data, length,
+ HCI_MAX_EXT_AD_LENGTH);
u8 len;
struct adv_info *adv = NULL;
int err;
- memset(&pdu, 0, sizeof(pdu));
-
if (instance) {
adv = hci_find_adv_instance(hdev, instance);
if (!adv || !adv->adv_data_changed)
return 0;
}
- len = eir_create_adv_data(hdev, instance, pdu.data);
+ len = eir_create_adv_data(hdev, instance, pdu->data);
- pdu.cp.length = len;
- pdu.cp.handle = instance;
- pdu.cp.operation = LE_SET_ADV_DATA_OP_COMPLETE;
- pdu.cp.frag_pref = LE_SET_ADV_DATA_NO_FRAG;
+ pdu->length = len;
+ pdu->handle = instance;
+ pdu->operation = LE_SET_ADV_DATA_OP_COMPLETE;
+ pdu->frag_pref = LE_SET_ADV_DATA_NO_FRAG;
err = __hci_cmd_sync_status(hdev, HCI_OP_LE_SET_EXT_ADV_DATA,
- sizeof(pdu.cp) + len, &pdu.cp,
+ struct_size(pdu, data, len), pdu,
HCI_CMD_TIMEOUT);
if (err)
return err;
@@ -1760,7 +1748,7 @@ static int hci_set_ext_adv_data_sync(struct hci_dev *hdev, u8 instance)
if (adv) {
adv->adv_data_changed = false;
} else {
- memcpy(hdev->adv_data, pdu.data, len);
+ memcpy(hdev->adv_data, pdu->data, len);
hdev->adv_data_len = len;
}
@@ -6496,10 +6484,8 @@ static int hci_le_create_conn_sync(struct hci_dev *hdev, void *data)
int hci_le_create_cis_sync(struct hci_dev *hdev)
{
- struct {
- struct hci_cp_le_create_cis cp;
- struct hci_cis cis[0x1f];
- } cmd;
+ DEFINE_FLEX(struct hci_cp_le_create_cis, cmd, cis, num_cis, 0x1f);
+ size_t aux_num_cis = 0;
struct hci_conn *conn;
u8 cig = BT_ISO_QOS_CIG_UNSET;
@@ -6526,8 +6512,6 @@ int hci_le_create_cis_sync(struct hci_dev *hdev)
* remains pending.
*/
- memset(&cmd, 0, sizeof(cmd));
-
hci_dev_lock(hdev);
rcu_read_lock();
@@ -6564,7 +6548,7 @@ int hci_le_create_cis_sync(struct hci_dev *hdev)
goto done;
list_for_each_entry_rcu(conn, &hdev->conn_hash.list, list) {
- struct hci_cis *cis = &cmd.cis[cmd.cp.num_cis];
+ struct hci_cis *cis = &cmd->cis[aux_num_cis];
if (hci_conn_check_create_cis(conn) ||
conn->iso_qos.ucast.cig != cig)
@@ -6573,25 +6557,25 @@ int hci_le_create_cis_sync(struct hci_dev *hdev)
set_bit(HCI_CONN_CREATE_CIS, &conn->flags);
cis->acl_handle = cpu_to_le16(conn->parent->handle);
cis->cis_handle = cpu_to_le16(conn->handle);
- cmd.cp.num_cis++;
+ aux_num_cis++;
- if (cmd.cp.num_cis >= ARRAY_SIZE(cmd.cis))
+ if (aux_num_cis >= 0x1f)
break;
}
+ cmd->num_cis = aux_num_cis;
done:
rcu_read_unlock();
hci_dev_unlock(hdev);
- if (!cmd.cp.num_cis)
+ if (!aux_num_cis)
return 0;
/* Wait for HCI_LE_CIS_Established */
return __hci_cmd_sync_status_sk(hdev, HCI_OP_LE_CREATE_CIS,
- sizeof(cmd.cp) + sizeof(cmd.cis[0]) *
- cmd.cp.num_cis, &cmd,
- HCI_EVT_LE_CIS_ESTABLISHED,
+ struct_size(cmd, cis, cmd->num_cis),
+ cmd, HCI_EVT_LE_CIS_ESTABLISHED,
conn->conn_timeout, NULL);
}
--
2.34.1On Fri, Apr 26, 2024 at 04:52:46PM -0600, Gustavo A. R. Silva wrote:
> Prepare for the coming implementation by GCC and Clang of the
> __counted_by attribute. Flexible array members annotated with
> __counted_by can have their accesses bounds-checked at run-time
> via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE
> (for strcpy/memcpy-family functions).
>
> Also, -Wflex-array-member-not-at-end is coming in GCC-14, and we are
> getting ready to enable it globally.
>
> So, use the `DEFINE_FLEX()` helper for multiple on-stack definitions
> 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.
>
> Notice that, due to the use of `__counted_by()` in `struct
> hci_cp_le_create_cis`, the for loop in function `hci_cs_le_create_cis()`
> had to be modified. Once the index `i`, through which `cp->cis[i]` is
> accessed, falls in the interval [0, cp->num_cis), `cp->num_cis` cannot
> be decremented all the way down to zero while accessing `cp->cis[]`:
>
> net/bluetooth/hci_event.c:4310:
> 4310 for (i = 0; cp->num_cis; cp->num_cis--, i++) {
> ...
> 4314 handle = __le16_to_cpu(cp->cis[i].cis_handle);
>
> otherwise, only half (one iteration before `cp->num_cis == i`) or half
> plus one (one iteration before `cp->num_cis < i`) of the items in the
> array will be accessed before running into an out-of-bounds issue. So,
> in order to avoid this, set `cp->num_cis` to zero just after the for
> loop.
>
> Also, make use of `aux_num_cis` variable to update `cmd->num_cis` after
> a `list_for_each_entry_rcu()` loop.
>
> With these changes, fix the following warnings:
> net/bluetooth/hci_sync.c:1239:56: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> net/bluetooth/hci_sync.c:1415:51: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> net/bluetooth/hci_sync.c:1731:51: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> net/bluetooth/hci_sync.c:6497:45: 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@kernel.org>
> ---
> Changes in v2:
> - Update `cmd->num_cis` after `list_for_each_entry_rcu()` loop.
>
> v1:
> - Link: https://lore.kernel.org/linux-hardening/ZiwqqZCa7PK9bzCX@neat/
>
> include/net/bluetooth/hci.h | 8 ++--
> net/bluetooth/hci_event.c | 3 +-
> net/bluetooth/hci_sync.c | 84 +++++++++++++++----------------------
> 3 files changed, 40 insertions(+), 55 deletions(-)
>
> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> index fe23e862921d..c4c6b8810701 100644
> --- a/include/net/bluetooth/hci.h
> +++ b/include/net/bluetooth/hci.h
> @@ -2026,7 +2026,7 @@ struct hci_cp_le_set_ext_adv_data {
> __u8 operation;
> __u8 frag_pref;
> __u8 length;
> - __u8 data[];
> + __u8 data[] __counted_by(length);
> } __packed;
I noticed some of the other structs here aren't flexible arrays, so it
made me go take a look at these ones. I see that the only user of struct
hci_cp_le_set_ext_adv_data uses a fixed-size array:
struct {
struct hci_cp_le_set_ext_adv_data cp;
u8 data[HCI_MAX_EXT_AD_LENGTH];
} pdu;
Let's just change this from a flex array to a fixed-size array?
>
> #define HCI_OP_LE_SET_EXT_SCAN_RSP_DATA 0x2038
> @@ -2035,7 +2035,7 @@ struct hci_cp_le_set_ext_scan_rsp_data {
> __u8 operation;
> __u8 frag_pref;
> __u8 length;
> - __u8 data[];
> + __u8 data[] __counted_by(length);
> } __packed;
Same for this one:
struct {
struct hci_cp_le_set_ext_scan_rsp_data cp;
u8 data[HCI_MAX_EXT_AD_LENGTH];
} pdu;
>
> #define HCI_OP_LE_SET_EXT_ADV_ENABLE 0x2039
> @@ -2061,7 +2061,7 @@ struct hci_cp_le_set_per_adv_data {
> __u8 handle;
> __u8 operation;
> __u8 length;
> - __u8 data[];
> + __u8 data[] __counted_by(length);
> } __packed;
And this one. :P
struct {
struct hci_cp_le_set_per_adv_data cp;
u8 data[HCI_MAX_PER_AD_LENGTH];
} pdu;
>
> #define HCI_OP_LE_SET_PER_ADV_ENABLE 0x2040
> @@ -2162,7 +2162,7 @@ struct hci_cis {
>
> struct hci_cp_le_create_cis {
> __u8 num_cis;
> - struct hci_cis cis[];
> + struct hci_cis cis[] __counted_by(num_cis);
> } __packed;
This one isn't as obvious, so I'd say keep your changes for this one.
>
> #define HCI_OP_LE_REMOVE_CIG 0x2065
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index 9a38e155537e..9a7ca084302e 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -4307,7 +4307,7 @@ static void hci_cs_le_create_cis(struct hci_dev *hdev, u8 status)
> hci_dev_lock(hdev);
>
> /* Remove connection if command failed */
> - for (i = 0; cp->num_cis; cp->num_cis--, i++) {
> + for (i = 0; i < cp->num_cis; i++) {
> struct hci_conn *conn;
> u16 handle;
>
> @@ -4323,6 +4323,7 @@ static void hci_cs_le_create_cis(struct hci_dev *hdev, u8 status)
> hci_conn_del(conn);
> }
> }
> + cp->num_cis = 0;
Yeah, this loop never leaves early, and if it did, it processing the
array forward, so having num_cis reduced during the loop iteration
doesn't make sense. What you have looks right to me!
>
> if (pending)
> hci_le_create_cis_pending(hdev);
> diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
> index 9092b4d59545..6e15594d3565 100644
> --- a/net/bluetooth/hci_sync.c
> +++ b/net/bluetooth/hci_sync.c
> @@ -1235,31 +1235,27 @@ int hci_setup_ext_adv_instance_sync(struct hci_dev *hdev, u8 instance)
>
> static int hci_set_ext_scan_rsp_data_sync(struct hci_dev *hdev, u8 instance)
> {
> - struct {
> - struct hci_cp_le_set_ext_scan_rsp_data cp;
> - u8 data[HCI_MAX_EXT_AD_LENGTH];
> - } pdu;
> + DEFINE_FLEX(struct hci_cp_le_set_ext_scan_rsp_data, pdu, data, length,
> + HCI_MAX_EXT_AD_LENGTH);
> u8 len;
> struct adv_info *adv = NULL;
> int err;
>
> - memset(&pdu, 0, sizeof(pdu));
These become much easier, just:
struct hci_cp_le_set_ext_scan_rsp_data cp = { };
etc...
--
Kees Cook
>> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
>> index fe23e862921d..c4c6b8810701 100644
>> --- a/include/net/bluetooth/hci.h
>> +++ b/include/net/bluetooth/hci.h
>> @@ -2026,7 +2026,7 @@ struct hci_cp_le_set_ext_adv_data {
>> __u8 operation;
>> __u8 frag_pref;
>> __u8 length;
>> - __u8 data[];
>> + __u8 data[] __counted_by(length);
>> } __packed;
>
> I noticed some of the other structs here aren't flexible arrays, so it
> made me go take a look at these ones. I see that the only user of struct
> hci_cp_le_set_ext_adv_data uses a fixed-size array:
>
> struct {
> struct hci_cp_le_set_ext_adv_data cp;
> u8 data[HCI_MAX_EXT_AD_LENGTH];
> } pdu;
>
> Let's just change this from a flex array to a fixed-size array?
mmh... not sure about this. It would basically mean reverting this commit:
c9ed0a707730 ("Bluetooth: Fix Set Extended (Scan Response) Data")
--
Gustavo
On Mon, Apr 29, 2024 at 01:50:46PM -0600, Gustavo A. R. Silva wrote:
>
> > > diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> > > index fe23e862921d..c4c6b8810701 100644
> > > --- a/include/net/bluetooth/hci.h
> > > +++ b/include/net/bluetooth/hci.h
> > > @@ -2026,7 +2026,7 @@ struct hci_cp_le_set_ext_adv_data {
> > > __u8 operation;
> > > __u8 frag_pref;
> > > __u8 length;
> > > - __u8 data[];
> > > + __u8 data[] __counted_by(length);
> > > } __packed;
> >
> > I noticed some of the other structs here aren't flexible arrays, so it
> > made me go take a look at these ones. I see that the only user of struct
> > hci_cp_le_set_ext_adv_data uses a fixed-size array:
> >
> > struct {
> > struct hci_cp_le_set_ext_adv_data cp;
> > u8 data[HCI_MAX_EXT_AD_LENGTH];
> > } pdu;
> >
> > Let's just change this from a flex array to a fixed-size array?
>
> mmh... not sure about this. It would basically mean reverting this commit:
>
> c9ed0a707730 ("Bluetooth: Fix Set Extended (Scan Response) Data")
That change doesn't seem to need to make them flex arrays, though --
there's no savings at all (the same amount is stack allocated).
Anyway, not a big deal, I guess. It's an improvement to be using
__counted_by, so good! :)
Reviewed-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
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