From: "Gustavo A. R. Silva"
stable inclusion
from stable-5.10
category: feature
commit:8128d3aac0ee3420ede34950c9c0ef9ee118bec9
issue: #I4919J
--------------------------------
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
Link: https://lore.kernel.org/r/20200309202327.GA8813@embeddedor
Signed-off-by: Kees Cook
(cherry picked from commit 8128d3aac0ee3420ede34950c9c0ef9ee118bec9)
Signed-off-by: roger
---
fs/pstore/ram_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index 4a947bb60210..b5cd09ed2212 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -33,7 +33,7 @@ struct persistent_ram_buffer {
uint32_t sig;
atomic_t start;
atomic_t size;
- uint8_t data[0];
+ uint8_t data[];
};
#define PERSISTENT_RAM_SIG (0x43474244) /* DBGC */
--
2.17.1
