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@xxxxxxxxxxxxxx>
---
fs/select.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/select.c b/fs/select.c
index 11d0285d46b7..f38a8a7480f7 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -97,7 +97,7 @@ u64 select_estimate_accuracy(struct timespec64 *tv)
struct poll_table_page {
struct poll_table_page * next;
struct poll_table_entry * entry;
- struct poll_table_entry entries[0];
+ struct poll_table_entry entries[];
};
#define POLL_TABLE_FULL(table) \
@@ -826,7 +826,7 @@ SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
struct poll_list {
struct poll_list *next;
int len;
- struct pollfd entries[0];
+ struct pollfd entries[];
};
#define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
--
2.25.0
