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7593f4c53c
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>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
49 lines
997 B
C
49 lines
997 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (C) 2012 Red Hat. All rights reserved.
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*/
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#ifndef BTRFS_RCU_STRING_H
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#define BTRFS_RCU_STRING_H
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struct rcu_string {
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struct rcu_head rcu;
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char str[];
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};
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static inline struct rcu_string *rcu_string_strdup(const char *src, gfp_t mask)
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{
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size_t len = strlen(src) + 1;
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struct rcu_string *ret = kzalloc(sizeof(struct rcu_string) +
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(len * sizeof(char)), mask);
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if (!ret)
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return ret;
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strncpy(ret->str, src, len);
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return ret;
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}
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static inline void rcu_string_free(struct rcu_string *str)
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{
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if (str)
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kfree_rcu(str, rcu);
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}
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#define printk_in_rcu(fmt, ...) do { \
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rcu_read_lock(); \
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printk(fmt, __VA_ARGS__); \
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rcu_read_unlock(); \
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} while (0)
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#define printk_ratelimited_in_rcu(fmt, ...) do { \
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rcu_read_lock(); \
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printk_ratelimited(fmt, __VA_ARGS__); \
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rcu_read_unlock(); \
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} while (0)
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#define rcu_str_deref(rcu_str) ({ \
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struct rcu_string *__str = rcu_dereference(rcu_str); \
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__str->str; \
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})
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#endif
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