From 06ccf63da5d8e90e4dff8b741972a9b279b5bf4c Mon Sep 17 00:00:00 2001
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Mon, 23 Mar 2020 19:38:18 -0500
Subject: [PATCH] tpm_eventlog.h: Replace zero-length array with flexible-array
member
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 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
include/linux/tpm_eventlog.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h
index 131ea1bad458be..c253461b1c4e66 100644
--- a/include/linux/tpm_eventlog.h
+++ b/include/linux/tpm_eventlog.h
@@ -28,7 +28,7 @@ struct tcpa_event {
u32 event_type;
u8 pcr_value[20]; /* SHA1 */
u32 event_size;
- u8 event_data[0];
+ u8 event_data[];
};
enum tcpa_event_types {
@@ -55,7 +55,7 @@ enum tcpa_event_types {
struct tcpa_pc_event {
u32 event_id;
u32 event_size;
- u8 event_data[0];
+ u8 event_data[];
};
enum tcpa_pc_event_ids {
@@ -102,7 +102,7 @@ struct tcg_pcr_event {
struct tcg_event_field {
u32 event_size;
- u8 event[0];
+ u8 event[];
} __packed;
struct tcg_pcr_event2_head {
--
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