diff options
| author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 14:22:10 -0500 |
|---|---|---|
| committer | Song Liu <songliubraving@fb.com> | 2020-05-13 12:02:23 -0700 |
| commit | 358369f03ac94637c9fd9d8f94a2dfde86b9f25f (patch) | |
| tree | aad637516aada9aff42bad4332d9b442d54394df | |
| parent | 3f99980c8f70bc56584450c0a69973eef7b65913 (diff) | |
md/raid1: 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: Song Liu <songliubraving@fb.com>
| -rw-r--r-- | drivers/md/md-linear.h | 2 | ||||
| -rw-r--r-- | drivers/md/raid1.h | 2 | ||||
| -rw-r--r-- | drivers/md/raid10.h | 2 |
3 files changed, 3 insertions, 3 deletions
diff --git a/drivers/md/md-linear.h b/drivers/md/md-linear.h index 8381d651d4ed..24e97db50ebb 100644 --- a/drivers/md/md-linear.h +++ b/drivers/md/md-linear.h @@ -12,6 +12,6 @@ struct linear_conf struct rcu_head rcu; sector_t array_sectors; int raid_disks; /* a copy of mddev->raid_disks */ - struct dev_info disks[0]; + struct dev_info disks[]; }; #endif diff --git a/drivers/md/raid1.h b/drivers/md/raid1.h index e7ccad898736..b7eb09e8c025 100644 --- a/drivers/md/raid1.h +++ b/drivers/md/raid1.h @@ -180,7 +180,7 @@ struct r1bio { * if the IO is in WRITE direction, then multiple bios are used. * We choose the number when they are allocated. */ - struct bio *bios[0]; + struct bio *bios[]; /* DO NOT PUT ANY NEW FIELDS HERE - bios array is contiguously alloced*/ }; diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h index d3eaaf3eb1bc..79cd2b7d3128 100644 --- a/drivers/md/raid10.h +++ b/drivers/md/raid10.h @@ -153,7 +153,7 @@ struct r10bio { }; sector_t addr; int devnum; - } devs[0]; + } devs[]; }; /* bits for r10bio.state */ |