diff options
| author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 13:51:38 -0500 |
|---|---|---|
| committer | Ilya Dryomov <idryomov@gmail.com> | 2020-06-01 13:22:53 +0200 |
| commit | 53ab8e7cd2d47594e68951994ac083d30f82fce4 (patch) | |
| tree | de8a33ef708a79bf5f92a24d51918cac763e34a8 | |
| parent | dffdcd71458e699e839f0bf47c3d42d64210b939 (diff) | |
libceph, rbd: 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>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
| -rw-r--r-- | drivers/block/rbd_types.h | 2 | ||||
| -rw-r--r-- | include/linux/ceph/mon_client.h | 2 | ||||
| -rw-r--r-- | include/linux/crush/crush.h | 2 |
3 files changed, 3 insertions, 3 deletions
diff --git a/drivers/block/rbd_types.h b/drivers/block/rbd_types.h index ac98ab6ccd3b..a600e0eb6b6f 100644 --- a/drivers/block/rbd_types.h +++ b/drivers/block/rbd_types.h @@ -93,7 +93,7 @@ struct rbd_image_header_ondisk { __le32 snap_count; __le32 reserved; __le64 snap_names_len; - struct rbd_image_snap_ondisk snaps[0]; + struct rbd_image_snap_ondisk snaps[]; } __attribute__((packed)); diff --git a/include/linux/ceph/mon_client.h b/include/linux/ceph/mon_client.h index dbb8a6959a73..ce4ffeb384d7 100644 --- a/include/linux/ceph/mon_client.h +++ b/include/linux/ceph/mon_client.h @@ -19,7 +19,7 @@ struct ceph_monmap { struct ceph_fsid fsid; u32 epoch; u32 num_mon; - struct ceph_entity_inst mon_inst[0]; + struct ceph_entity_inst mon_inst[]; }; struct ceph_mon_client; diff --git a/include/linux/crush/crush.h b/include/linux/crush/crush.h index 54741295c70b..38b0e4d50ed9 100644 --- a/include/linux/crush/crush.h +++ b/include/linux/crush/crush.h @@ -87,7 +87,7 @@ struct crush_rule_mask { struct crush_rule { __u32 len; struct crush_rule_mask mask; - struct crush_rule_step steps[0]; + struct crush_rule_step steps[]; }; #define crush_rule_size(len) (sizeof(struct crush_rule) + \ |