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author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 13:57:10 -0500 |
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committer | David Howells <dhowells@redhat.com> | 2020-06-02 17:22:31 +0100 |
commit | 2ce113fa525faf62fc308a10d1e5af07456b7460 (patch) | |
tree | d483a8b138ee383124e5f3f1aeade3d970ca23cf | |
parent | 352780b61ebbd5fef845714c17246e1647c6904a (diff) | |
download | linux-2ce113fa525faf62fc308a10d1e5af07456b7460.tar.gz linux-2ce113fa525faf62fc308a10d1e5af07456b7460.tar.bz2 linux-2ce113fa525faf62fc308a10d1e5af07456b7460.zip |
KEYS: 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: David Howells <dhowells@redhat.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
-rw-r--r-- | include/keys/user-type.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/keys/user-type.h b/include/keys/user-type.h index be61fcddc02a..386c31432789 100644 --- a/include/keys/user-type.h +++ b/include/keys/user-type.h @@ -27,7 +27,7 @@ struct user_key_payload { struct rcu_head rcu; /* RCU destructor */ unsigned short datalen; /* length of this data */ - char data[0] __aligned(__alignof__(u64)); /* actual data */ + char data[] __aligned(__alignof__(u64)); /* actual data */ }; extern struct key_type key_type_user; |