From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH][next] fs/binfmt_elf.c: Replace zero-length array with flexible-array member
Date: Fri, 6 Mar 2020 10:47:12 -0600 [thread overview]
Message-ID: <20200306164712.GA21930@embeddedor> (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>
---
fs/binfmt_elf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 13f25e241ac4..6a7f1fc26eb1 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1664,7 +1664,7 @@ struct elf_thread_core_info {
struct elf_thread_core_info *next;
struct task_struct *task;
struct elf_prstatus prstatus;
- struct memelfnote notes[0];
+ struct memelfnote notes[];
};
struct elf_note_info {
--
2.25.0
reply other threads:[~2020-03-06 16:44 UTC|newest]
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