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author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 13:51:58 -0500 |
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committer | Mike Snitzer <snitzer@redhat.com> | 2020-05-20 17:09:44 -0400 |
commit | b18ae8dd9d7685233d7be472c043c545f18d015a (patch) | |
tree | 29ed7853e416e1d8aa1a55a769eaf8942668e063 /drivers/md/dm-raid1.c | |
parent | bd5c40313a1467e4683d92456fc5219d94823f24 (diff) | |
download | linux-b18ae8dd9d7685233d7be472c043c545f18d015a.tar.gz linux-b18ae8dd9d7685233d7be472c043c545f18d015a.tar.bz2 linux-b18ae8dd9d7685233d7be472c043c545f18d015a.zip |
dm: 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: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/dm-raid1.c')
-rw-r--r-- | drivers/md/dm-raid1.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c index 089aed57e083..2f655d9f4200 100644 --- a/drivers/md/dm-raid1.c +++ b/drivers/md/dm-raid1.c @@ -83,7 +83,7 @@ struct mirror_set { struct work_struct trigger_event; unsigned nr_mirrors; - struct mirror mirror[0]; + struct mirror mirror[]; }; DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(raid1_resync_throttle, |