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authorGustavo A. R. Silva <gustavoars@kernel.org>2020-05-07 14:26:52 -0500
committerRichard Weinberger <richard@nod.at>2020-06-02 22:38:00 +0200
commitf6e8c474390be2e6f5bd0b8966e19958214609ff (patch)
tree02e326d53cfcd189bf72bd68886c67d49258702e /arch/um/drivers
parent54ebe4060fe6c4ab76c79354417612ac9cf4f95e (diff)
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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/drivers')
-rw-r--r--arch/um/drivers/vector_kern.h2
-rw-r--r--arch/um/drivers/vhost_user.h2
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 {