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| author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 14:26:52 -0500 |
|---|---|---|
| committer | Richard Weinberger <richard@nod.at> | 2020-06-02 22:38:00 +0200 |
| commit | f6e8c474390be2e6f5bd0b8966e19958214609ff (patch) | |
| tree | 02e326d53cfcd189bf72bd68886c67d49258702e /arch/um | |
| parent | 54ebe4060fe6c4ab76c79354417612ac9cf4f95e (diff) | |
| download | linux-f6e8c474390be2e6f5bd0b8966e19958214609ff.tar.gz | |
um: virtio: 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: Richard Weinberger <richard@nod.at>
Diffstat (limited to 'arch/um')
| -rw-r--r-- | arch/um/drivers/vector_kern.h | 2 | ||||
| -rw-r--r-- | arch/um/drivers/vhost_user.h | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/arch/um/drivers/vector_kern.h b/arch/um/drivers/vector_kern.h index d0159082faf0..8fff93a75a92 100644 --- a/arch/um/drivers/vector_kern.h +++ b/arch/um/drivers/vector_kern.h @@ -129,7 +129,7 @@ struct vector_private { struct vector_estats estats; struct sock_fprog *bpf; - char user[0]; + char user[]; }; extern int build_transport_data(struct vector_private *vp); diff --git a/arch/um/drivers/vhost_user.h b/arch/um/drivers/vhost_user.h index 6c71b6005177..6f147cd3c9f7 100644 --- a/arch/um/drivers/vhost_user.h +++ b/arch/um/drivers/vhost_user.h @@ -78,7 +78,7 @@ struct vhost_user_config { u32 offset; u32 size; u32 flags; - u8 payload[0]; /* Variable length */ + u8 payload[]; /* Variable length */ } __packed; struct vhost_user_vring_state { |