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b90feaff2a
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 7649773293 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
77 lines
1.6 KiB
C
77 lines
1.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* net/sched/em_nbyte.c N-Byte ematch
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*
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* Authors: Thomas Graf <tgraf@suug.ch>
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*/
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#include <linux/gfp.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/skbuff.h>
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#include <linux/tc_ematch/tc_em_nbyte.h>
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#include <net/pkt_cls.h>
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struct nbyte_data {
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struct tcf_em_nbyte hdr;
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char pattern[];
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};
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static int em_nbyte_change(struct net *net, void *data, int data_len,
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struct tcf_ematch *em)
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{
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struct tcf_em_nbyte *nbyte = data;
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if (data_len < sizeof(*nbyte) ||
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data_len < (sizeof(*nbyte) + nbyte->len))
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return -EINVAL;
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em->datalen = sizeof(*nbyte) + nbyte->len;
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em->data = (unsigned long)kmemdup(data, em->datalen, GFP_KERNEL);
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if (em->data == 0UL)
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return -ENOBUFS;
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return 0;
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}
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static int em_nbyte_match(struct sk_buff *skb, struct tcf_ematch *em,
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struct tcf_pkt_info *info)
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{
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struct nbyte_data *nbyte = (struct nbyte_data *) em->data;
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unsigned char *ptr = tcf_get_base_ptr(skb, nbyte->hdr.layer);
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ptr += nbyte->hdr.off;
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if (!tcf_valid_offset(skb, ptr, nbyte->hdr.len))
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return 0;
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return !memcmp(ptr, nbyte->pattern, nbyte->hdr.len);
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}
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static struct tcf_ematch_ops em_nbyte_ops = {
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.kind = TCF_EM_NBYTE,
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.change = em_nbyte_change,
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.match = em_nbyte_match,
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.owner = THIS_MODULE,
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.link = LIST_HEAD_INIT(em_nbyte_ops.link)
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};
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static int __init init_em_nbyte(void)
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{
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return tcf_em_register(&em_nbyte_ops);
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}
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static void __exit exit_em_nbyte(void)
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{
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tcf_em_unregister(&em_nbyte_ops);
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}
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MODULE_LICENSE("GPL");
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module_init(init_em_nbyte);
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module_exit(exit_em_nbyte);
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MODULE_ALIAS_TCF_EMATCH(TCF_EM_NBYTE);
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