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tpm_eventlog.h: 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>
This commit is contained in:
Gustavo A. R. Silva 2020-03-23 19:38:18 -05:00
parent 4ea19ecf32
commit 06ccf63da5
1 changed files with 3 additions and 3 deletions
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6
include/linux/tpm_eventlog.h
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@ -28,7 +28,7 @@ struct tcpa_event {
u32 event_type; u32 event_type;
u8 pcr_value[20]; /* SHA1 */ u8 pcr_value[20]; /* SHA1 */
u32 event_size; u32 event_size;
u8 event_data[0]; u8 event_data[];
}; };
enum tcpa_event_types { enum tcpa_event_types {
@ -55,7 +55,7 @@ enum tcpa_event_types {
struct tcpa_pc_event { struct tcpa_pc_event {
u32 event_id; u32 event_id;
u32 event_size; u32 event_size;
u8 event_data[0]; u8 event_data[];
}; };
enum tcpa_pc_event_ids { enum tcpa_pc_event_ids {
@ -102,7 +102,7 @@ struct tcg_pcr_event {
struct tcg_event_field { struct tcg_event_field {
u32 event_size; u32 event_size;
u8 event[0]; u8 event[];
} __packed; } __packed;
struct tcg_pcr_event2_head { struct tcg_pcr_event2_head {