Skip to contentSkip to conversation

hv: hyperv.h: Replace one-element array with flexible-array in struct icmsg_negotiate

PATCH Applied Gustavo A. R. Silva 3 participants 3 messages Feb 1, 2021

Subsystems (2)
Hyper-V/Azure core and drivers Microsoft MANA RDMA driver
lore
Share & tools
lore

Gustavo A. R. Silva

author
#0 lore raw

PATCH 1/1 hv: hyperv.h: Replace one-element array with flexible-array in struct icmsg_negotiate

There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2].

Refactor the code according to the use of a flexible-array member in struct icmsg_negotiate, instead of a one-element array.

Also, this helps the ongoing efforts to enable -Warray-bounds and fix the following warnings:

drivers/hv/channel_mgmt.c:315:23: warning: array subscript 1 is above array bounds of ‘struct ic_version[1]’ [-Warray-bounds] drivers/hv/channel_mgmt.c:316:23: warning: array subscript 1 is above array bounds of ‘struct ic_version[1]’ [-Warray-bounds]

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays

Link https://github.com/KSPP/linux/issues/79
Link https://github.com/KSPP/linux/issues/109
Signed-off-by Gustavo A. R. Silva <[email protected]>
---
 include/linux/hyperv.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
include/linux/hyperv.h +2 -2
index f0d48a368f13..7877746f1077 100644
@@ -1528,14 +1528,14 @@ struct icmsg_hdr {
 #define IC_VERSION_NEGOTIATION_MAX_VER_COUNT 100
 #define ICMSG_HDR (sizeof(struct vmbuspipe_hdr) + sizeof(struct icmsg_hdr))
 #define ICMSG_NEGOTIATE_PKT_SIZE(icframe_vercnt, icmsg_vercnt) \
-	(ICMSG_HDR + offsetof(struct icmsg_negotiate, icversion_data) + \
+	(ICMSG_HDR + sizeof(struct icmsg_negotiate) + \
 	 (((icframe_vercnt) + (icmsg_vercnt)) * sizeof(struct ic_version)))
 
 struct icmsg_negotiate {
 	u16 icframe_vercnt;
 	u16 icmsg_vercnt;
 	u32 reserved;
-	struct ic_version icversion_data[1]; /* any size array */
+	struct ic_version icversion_data[]; /* any size array */
 } __packed;
 
 struct shutdown_msg_data {
Signature · 1 line
2.27.0
Reviewed-by on v1 1/1
#1 lore raw

From: Gustavo A. R. Silva <[email protected]> Sent: Monday, February 1, 2021 9:44 AM

Quoted 47 lines

There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use "flexible array members"[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2].

Refactor the code according to the use of a flexible-array member in struct icmsg_negotiate, instead of a one-element array.

Also, this helps the ongoing efforts to enable -Warray-bounds and fix the following warnings:

drivers/hv/channel_mgmt.c:315:23: warning: array subscript 1 is above array bounds of 'struct ic_version[1]' [-Warray-bounds] drivers/hv/channel_mgmt.c:316:23: warning: array subscript 1 is above array bounds of 'struct ic_version[1]' [-Warray-bounds]

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays

Link https://github.com/KSPP/linux/issues/79
Link https://github.com/KSPP/linux/issues/109
Signed-off-by Gustavo A. R. Silva <[email protected]>
---
 include/linux/hyperv.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
include/linux/hyperv.h +2 -3
index f0d48a368f13..7877746f1077 100644
@@ -1528,14 +1528,14 @@ struct icmsg_hdr {
 #define IC_VERSION_NEGOTIATION_MAX_VER_COUNT 100
 #define ICMSG_HDR (sizeof(struct vmbuspipe_hdr) + sizeof(struct icmsg_hdr))
 #define ICMSG_NEGOTIATE_PKT_SIZE(icframe_vercnt, icmsg_vercnt) \
-	(ICMSG_HDR + offsetof(struct icmsg_negotiate, icversion_data) + \
+	(ICMSG_HDR + sizeof(struct icmsg_negotiate) + \
 	 (((icframe_vercnt) + (icmsg_vercnt)) * sizeof(struct ic_version)))
 
 struct icmsg_negotiate {
 	u16 icframe_vercnt;
 	u16 icmsg_vercnt;
 	u32 reserved;
-	struct ic_version icversion_data[1]; /* any size array */
+	struct ic_version icversion_data[]; /* any size array */
 } __packed;
 
 struct shutdown_msg_data {
--
Quoted 1 line

2.27.0

Reviewed-by Michael Kelley <[email protected]>