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Bluetooth: Replace zero-length array with flexible-array member

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The current codebase makes use of the zero-length array language
extension to the C90 standard, 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.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
This commit is contained in:
Gustavo A. R. Silva
2020-02-26 17:02:27 -06:00
committed by Marcel Holtmann
parent eed467b517
commit a7e454542b
8 changed files with 36 additions and 36 deletions
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10
net/bluetooth/a2mp.h
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@@ -36,14 +36,14 @@ struct a2mp_cmd {
__u8 code;
__u8 ident;
__le16 len;
__u8 data[0];
__u8 data[];
} __packed;
/* A2MP command codes */
#define A2MP_COMMAND_REJ 0x01
struct a2mp_cmd_rej {
__le16 reason;
__u8 data[0];
__u8 data[];
} __packed;
#define A2MP_DISCOVER_REQ 0x02
@@ -62,7 +62,7 @@ struct a2mp_cl {
struct a2mp_discov_rsp {
__le16 mtu;
__le16 ext_feat;
struct a2mp_cl cl[0];
struct a2mp_cl cl[];
} __packed;
#define A2MP_CHANGE_NOTIFY 0x04
@@ -93,7 +93,7 @@ struct a2mp_amp_assoc_req {
struct a2mp_amp_assoc_rsp {
__u8 id;
__u8 status;
__u8 amp_assoc[0];
__u8 amp_assoc[];
} __packed;
#define A2MP_CREATEPHYSLINK_REQ 0x0A
@@ -101,7 +101,7 @@ struct a2mp_amp_assoc_rsp {
struct a2mp_physlink_req {
__u8 local_id;
__u8 remote_id;
__u8 amp_assoc[0];
__u8 amp_assoc[];
} __packed;
#define A2MP_CREATEPHYSLINK_RSP 0x0B