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author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 13:43:56 -0500 |
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committer | John Johansen <john.johansen@canonical.com> | 2020-05-15 13:04:55 -0700 |
commit | fe9fd23e3b587c7ca9520717b213f88050c1d324 (patch) | |
tree | 19a983a7b1be3c2211c89741f719071d9cbc98df /security | |
parent | c27c6bd2c4d6b6bb779f9b722d5607993e1d5e5c (diff) | |
download | linux-fe9fd23e3b587c7ca9520717b213f88050c1d324.tar.gz linux-fe9fd23e3b587c7ca9520717b213f88050c1d324.tar.bz2 linux-fe9fd23e3b587c7ca9520717b213f88050c1d324.zip |
apparmor: 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: John Johansen <john.johansen@canonical.com>
Diffstat (limited to 'security')
-rw-r--r-- | security/apparmor/apparmorfs.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c index d7a179cdaa1e..d65324415980 100644 --- a/security/apparmor/apparmorfs.c +++ b/security/apparmor/apparmorfs.c @@ -807,7 +807,7 @@ static ssize_t query_label(char *buf, size_t buf_len, struct multi_transaction { struct kref count; ssize_t size; - char data[0]; + char data[]; }; #define MULTI_TRANSACTION_LIMIT (PAGE_SIZE - sizeof(struct multi_transaction)) |