From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Doug Ledford <dledford@redhat.com>, Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] IB/core, cache: Replace zero-length array with flexible-array member
Date: Wed, 12 Feb 2020 19:04:25 -0600 [thread overview]
Message-ID: <20200213010425.GA13068@embeddedor.com> (raw)
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>
---
drivers/infiniband/core/cache.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/infiniband/core/cache.c b/drivers/infiniband/core/cache.c
index 17bfedd24cc3..dedfbe27916f 100644
--- a/drivers/infiniband/core/cache.c
+++ b/drivers/infiniband/core/cache.c
@@ -46,7 +46,7 @@
struct ib_pkey_cache {
int table_len;
- u16 table[0];
+ u16 table[];
};
struct ib_update_work {
--
2.23.0
next reply other threads:[~2020-02-13 1:49 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-13 1:04 Gustavo A. R. Silva [this message]
2020-02-13 1:08 ` [PATCH] IB/core, cache: Replace zero-length array with flexible-array member Jason Gunthorpe
2020-02-13 18:36 ` Gustavo A. R. Silva
2020-02-13 18:37 ` Leon Romanovsky
2020-02-13 18:46 ` Gustavo A. R. Silva
2020-02-20 17:37 ` Jason Gunthorpe
2020-02-20 18:09 ` Gustavo A. R. Silva
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200213010425.GA13068@embeddedor.com \
--to=gustavo@embeddedor.com \
--cc=dledford@redhat.com \
--cc=jgg@ziepe.ca \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rdma@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).