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| author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 20:56:01 +0200 |
|---|---|---|
| committer | Masahiro Yamada <masahiroy@kernel.org> | 2020-05-25 17:03:16 +0200 |
| commit | 859c81750130844590a83eff847c6c55e2340ab1 (patch) | |
| tree | 659355f4f132172c4052fdd2a9f0c705e696d903 /scripts/mod | |
| parent | scripts: headers_install: Exit with error on config leak (diff) | |
| download | linux-859c81750130844590a83eff847c6c55e2340ab1.tar.xz linux-859c81750130844590a83eff847c6c55e2340ab1.zip | |
modpost,fixdep: Replace zero-length array with flexible-array
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 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'scripts/mod')
| -rw-r--r-- | scripts/mod/modpost.c | 2 | ||||
| -rw-r--r-- | scripts/mod/modpost.h | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 5c3c50c5ec52..4d4b979d76be 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -166,7 +166,7 @@ struct symbol { * (only for external modules) **/ unsigned int is_static:1; /* 1 if symbol is not global */ enum export export; /* Type of export */ - char name[0]; + char name[]; }; static struct symbol *symbolhash[SYMBOL_HASH_SIZE]; diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h index 60dca9b7106b..39f6c29fb568 100644 --- a/scripts/mod/modpost.h +++ b/scripts/mod/modpost.h @@ -111,7 +111,7 @@ buf_write(struct buffer *buf, const char *s, int len); struct namespace_list { struct namespace_list *next; - char namespace[0]; + char namespace[]; }; struct module { |