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2ce113fa52
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]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
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 <gustavoars@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
59 lines
1.9 KiB
C
59 lines
1.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/* user-type.h: User-defined key type
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*
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* Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#ifndef _KEYS_USER_TYPE_H
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#define _KEYS_USER_TYPE_H
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#include <linux/key.h>
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#include <linux/rcupdate.h>
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#ifdef CONFIG_KEYS
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/*****************************************************************************/
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/*
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* the payload for a key of type "user" or "logon"
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* - once filled in and attached to a key:
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* - the payload struct is invariant may not be changed, only replaced
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* - the payload must be read with RCU procedures or with the key semaphore
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* held
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* - the payload may only be replaced with the key semaphore write-locked
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* - the key's data length is the size of the actual data, not including the
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* payload wrapper
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*/
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struct user_key_payload {
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struct rcu_head rcu; /* RCU destructor */
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unsigned short datalen; /* length of this data */
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char data[] __aligned(__alignof__(u64)); /* actual data */
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};
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extern struct key_type key_type_user;
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extern struct key_type key_type_logon;
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struct key_preparsed_payload;
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extern int user_preparse(struct key_preparsed_payload *prep);
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extern void user_free_preparse(struct key_preparsed_payload *prep);
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extern int user_update(struct key *key, struct key_preparsed_payload *prep);
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extern void user_revoke(struct key *key);
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extern void user_destroy(struct key *key);
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extern void user_describe(const struct key *user, struct seq_file *m);
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extern long user_read(const struct key *key, char *buffer, size_t buflen);
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static inline const struct user_key_payload *user_key_payload_rcu(const struct key *key)
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{
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return (struct user_key_payload *)dereference_key_rcu(key);
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}
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static inline struct user_key_payload *user_key_payload_locked(const struct key *key)
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{
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return (struct user_key_payload *)dereference_key_locked((struct key *)key);
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}
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#endif /* CONFIG_KEYS */
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#endif /* _KEYS_USER_TYPE_H */
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